[Warning: Spoilers Ahead for Skul: The Hero Slayer]

The dark mirror is a mode that's unlocked after you finish the original game. There are ten levels in total (not counting your initial run); you unlock the next level as well as an equipment reward after you beat the final boss of your current level (the emperor and dark skul not required). The most prominent change in the dark mirror are the enemies; there are new enemies every two levels and all bosses have additional/modified attacks (the final boss, the first hero, has a modified second phase and doesn't have a third phase). You also unlock a variety of features as you progress, such as the Bone Offerings from Arachne, the dark abilities, the additional item in the black market, etc.

It can be quite challenging for a new player to encounter such new additions for the first time, and even for experienced players, it can be difficult to beat higher levels as enemies' health and damage increase drastically (the first boss in dark mirror level 10 has nearly five times the health he does in the original). Thus, it can be useful to learn some tips before you venture in. But then again, it's always encouraged to try out things yourself and see what works for you. These are just some tips and guides gathered from countless runs.

In this guide, I will recommend skulls, note useful items, as well as list out some key points/synergies. Enjoy and have fun!

Yours,
Will

While you can experiment with many different builds, it can be quite challenging to pass high dark mirror levels without some solid damage or synergy. Here are some of the best skulls you can try out:

Alchemist: Really strong magical skull; solid for dealing damage as well as being very versatile. The fire flask does decent damage and the freeze/stun flask is great for control. The "unstable summoning" skill, which you get after upgrading to Unique/Legendary, deals really good damage and covers basically the whole screen. After you beat Dark Mirror 7, you will be able to get the skull from the beginning. Safe and strong choice.

Frost Skull: The swap skill, hibernation, gives you two seconds of invincibility, which is incredibly useful in dark mirror runs. The final few bosses have some very wide-ranging and high-damaging attacks, and those two seconds can be a life saver. Plus, the skull dishes out decent damage and has strong control abilities, so a great pick overall. For skills I would prefer Glacial Sword and Charge over the other two.

Skeleton - Bomber: Quick and explosive. It's crucial to get the "Kaboom" skill (especially early on) for manual explosion, and for the other skill I would choose Ignite to boost damage. I prefer to use the skull as quickly as possible, and cycle explosions fast by swapping as soon as the cooldown's gone and hitting Ignite a few times before Kaboom. The huge explosion damage is really helpful for clearing up tough enemies and it's also very versatile for damage dealing. Solid Pick.

Ghoul: Healing is life-saving as most enemy attacks deal a lot of damage in the dark mirror. Once upgraded to at least Unique, Ghoul's meat chunk mechanics allows him to not only deal more physical damage but also heal portion of received damage. This can be paired with the dark ability "Piety" (see "Dark Abilities" in table of contents) and the revenge/relic inscription to form a very strong and easy healing build (see “Ghoul Healing Build” in "Builds" in the table of contents).

Werewolf: Really fast, has some invincibility, and deals good damage. The fact that you can chain skills makes it super versatile (although less when fighting a boss), and the Hunt skill gives you some crazy damage bonus. Beast Leap gives good mobility and invincibility, while the other two skills either chain or heal. Increase the movement and attack speed and you'll get a vicious killing machine. Keep in mind that two of the skills deal physical while the other two deal magical, so you're going to want to focus on one or make sure it's the skill you want for your build.

Skeleton - Shield: The shield mechanic acts as temporary hitpoints, and a little bonus hitpoints can never go amiss. The shield skull deals pretty good physical damage, and it can rack up shields quickly, which allows you to take more damage (or deal more damage; see "Shield Backlash Build" in "Builds").

Slave: This skull might not be for everybody, but for those who know how ot parry, this is the one for you. It has the ability to parry, which nullifies the damage (and when upgraded allows you to deal extra damage). Incredibly versatile, you can block out pretty much any attack if you can react in time, and the skull itself does pretty good damage on its own. If you've got the skills, then try Slave. Also ideal for hitless runs/achievements.

Alchemist + Frost Skull is almost always a solid pick; use "Unstable Summoning" from Alchemist to deal damage, and Frost Skull for control and invincibility. You can also switch out Frost for Bomber. Other good skulls include Great Warlock (the abyss meteor skill deals insane damage and covers an extreme range; good for one-shotting through normal rooms as well as bosses) and Living Armor (you can cycle skills quickly with the Flame Spirits gauge, and the skills themselves are strong as well).

You can either aim to have your skulls as the main damage source and focus items based on boosting damage, or make your play more items oriented (see "Items"). As long as you have high enough attack (and decent amount of hit points), most skulls should work (unless it's really bad). It's really up to you as to what you choose. However, if you've chosen a skull to invest in, make sure you don't switch halfway as you might not have enough resources to throw together a good build.

Here are some screenshots from some of my previous runs:

With the countless items in the game, it can be quite hard to choose what items to use. While some items are universally useful, most are really up to your specific build, so it’s important to keep that in mind when choosing items. Here, I’ll recommend some universal items that are consistently helpful/strong. Specific build items (like the spirit rings) will be included in the next part (“Builds”).

Solar Sword: Grants 40% physical damage increase. If you get Lunar Ring, the two items will combine to make Fulgent Dawn, which gives 80% increase to both physical and magical as well as a burst of damage every 50 seconds. If you’re able to duplicate it (with the slime npc), you will get Dawn of the Crimson Sun, which gives you a whopping 100% increase in physical damage. The same goes for Lunar Ring, but for magical damage. The stats is good and the burst of light has decent range and damage as well.

Golden Sword: You’re probably going to spend at least 7000 coins in one run, so the golden sword grants a guaranteed 70% increase in physical damage. For a rare item, the stat increase is pretty nice.

Ritual Staff: Gives 50% magical damage increase as well as 40% skill cooldown speed increase for balance skulls. If you’re using Frost & Alchemist (both are magical balance skulls), you have a constant skill cooldown increase. Plus, it works well with Nether Mana Suppressor, which boosts magical damage based on skill cooldown speed; you can reach 100% cooldown speed increase with the ritual staff’s 40% and the witch’s 60% upgrade (for balance skulls).

Nether Mana Suppressor: mentioned above. Maximum increases 120% magical damage; impressive stats increase and inscriptions.

Hope Slasher: Maximum grants 120% increase in physical damage. Works similarly to nether mana suppressor, but you need to consistently deal damage to get that 60%.

Stone Mask: Based on your skull’s rarity, the stone mask grants you extra gold. You can’t hurt with a little more gold; remember to switch it out at the end though.

Prohibited Book & Forbidden Sword: Both require you to deal damage to enemies (the book requires you to deal skill damage while the sword requires you to kill the enemy). Once you’re reached their quota, the items transform into more powerful ones with respective stats increase and effects (the sword gives extra attacks when you dash and attack, while the book summons tentacles/shockwaves/orbs after you use your skills a few times). Both give decent boosts to damage and their effects can be pretty useful. However, if you don’t think you can reach the quota before the final fight, then don’t get it (you have to deal skill damage 500 times or kill 300 enemies). If you get the item on the first/second/third map, you still have a chance.

Water Spirit Undine & Lake In A Bottle: If you’re able to get the both of them in one run, they will transform and grant you 110% increase in magical damage as well as a 45% increase in attack speed and a spirit. Pretty good stat boosts; also really useful for getting fairy tale inscriptions.

Olive Tree Cudgel: grants a variety of buffs; you’re pretty likely to get all of them through one run. Increase max HP by 80, summon earthquakes when using skills, increase physical damage by 100%, decrease damage received by 20% and boost damage dealt by 20%…not much to say here. Just look at the effects yourself.

Pot of Greed: Grants you 120% increase in both physical and magical damage if you’ve got 4 legendary skulls/items/quintessences. As you progress, 4 should be easy to reach, and when you reach it, the item grants you an extra random legendary. Essentially two legendary items in one with a massive damage increase. What’s not to love about it?

Voodoo Doll: grants you an extra life with a moderately small amount of hit points. An extra chance never hurts, right? After the one time it saves you, it grants you 60% increase in magical damage.


The Chosen Hero’s Circlet: A really strong item in general. Works similar to voodoo doll but better; when your hit points reach 15% or below, you are invincible for 7 seconds and have 50% amplified physical damage & 100% faster move speed. After the seven seconds, you recover hit points equal to the damage dealt to enemies during the time (up to 30%). The best thing is that it doesn’t break after that; after 60 seconds, the effect will be ready again. It only falls from adventurer fights (from the sword dude), however, and so it’s very rare.

Omen: Shard of Darkness with either Lunar Ring or Solar Sword: if you have Omen: Shard of Darkness and have Lunar Ring or Solar Sword, the items will combine and become either Omen: Solar Eclipse or Omen: Lunar Eclipse. The two items increase (respectively) physical or magical damage by 150% and grants you invincibility for 3 seconds with 1 hit point when you receive fatal damage (recharges after you defeat 50 enemies). The stats increase and fatal damage save is quite useful, but it does have the omen inscription, so use at your own risk (the omen inscription grants you negative effects based on the number of it; increase received damage, decrease max hit points, or one-hit death).

And now, for those equipments that are useful for specific scenarios and doesn’t really fit into large/popular builds:


Glacier Breaker: specifically boosts damage dealt to frozen enemies (use Frost Skull or Alchemist with Ice Flask). While the damage boost is decent, most freeze-dealing skulls aren’t that good at dealing damage themselves, and this renders the use of freeze as a main damage source to be niche. It really doesn’t feel that different when you use it, unfortunately, but a 30% damage increase is still no joke.

The Ring: does everything, but none of them are spectacular. Grants you stat boosts in almost everything from hit points to damage to skill cooldown, but none of the numbers are very impressive and is usually outshined by more specific items. However, if you’re starting early one or have an empty spot, then a little overall boost should do well.

Veiled Mask: decreases critical chance hugely but compensate with a 70% increase in critical damage. The 30% decrease means that if you want to have a critical hit, you have to bring it up with other items/buffs. Unless you are using a critical damage/rate build, use skulls that have automatically critical hits (e.g. samurai’s Single Slash) or use the Troll quintessence, which turns all attacks into critical hits for 5 seconds (that combo is actually quite deadly).

Dark abilities are a big part of the dark mirror levels; you can access them in between big chapters and you get the currency for them by defeating dark enemies, who are buffed normal enemies with an extra attack/mechanic. Some of the abilities are stronger than others, while others are less impressive. Here's a rundown of basically every ability:


Innate Power: boosts basic attack damage. Useful if you're doing a normal attack build, or your basic attack is your main power source.

Super Baby: boosts your max hit points. A little extra health can't hurt, right? Not super useful if you're aiming for absolute power and damage, but it fits in well with tanky builds, and if you've got an extra space, it can be a good choice.

Lethal Speed: when you land a critical hit, you have boosted attack and move speed. Probably specially designed for werewolf. Not very useful.

Coziness: grants cooldown speed and crit rate boost when you have a shield. Useful if you're doing a shield build, but otherwise somewhat useless.

Reckless Posture: boosts physical/magical damage and decreases incoming damage; effect multiplies five times for a few seconds when you're hit. Useful for ghoul healing build, otherwise not very practical.

Counterattack: when you dodge an attack, you gain boosted physical/magical damage. The boost it offers is quite practical, but it's not as flexible as some of the other boosts. I'd rather not choose it.

Lightweight: dash cooldown decreases when you defeat an enemy. Not sure which body part the developers used to think up this.

Shorthand/Hawkeye: boosts damage dealt to either close enemies (marked by a circle around you) or far away enemies (outside the circle). Shorthand is quite practical as you're very likely to be in close range with the enemy when you're fighting, but then again if you're using ranged skulls, Hawkeye might be a good option. Personally, neither shine out as very strong abilities, but you choose whether you need it or not.

Soul Strike: boosts skill damage dealt to enemies. Plain, simple and powerful. The damage boost won't affect the same enemy for two seconds, but it's only two seconds. C'mon. The max 75% damage boost is undeniable. Plus, it's pretty cheap. What are you waiting for?

Weakness Exposure: attacking enemies for a number of times will deal extra damage, Not very powerful or useful unless perhaps you're doing fast attack build.

Hard Shell: gain shields when entering a map. Useful for shield build.

Beast Blood: enhances damage for a while when you enter a map; if you defeat an enemy the time is reset. Can be used in normal rooms, but useless in boss fights. I would rather use something else.

King Slayer: instantly kill mini-bosses and bosses when they're at 10% hitpoints. Not immediately viable, but not useless.

Achievement: heal after you finish a map. If you're bad at the game, a little heal here and there won't hurt.

Electric field: create an electric field every time you deal 7 normal attacks. Useful for perhaps rapidity normal attack build. Not universally powerful.

Collection Desire: boosts physical/magical damage for every inscriptions with 2 or more. Inscrpitions with 2 or more shouldn't be hard to find, so this is a very solid and significant boost. Avoid if you don't have that much inscriptions though.

Last Resistance: an extra life with 25% hit points. Why not?

Piety: increases hit points recovery and boosts damage upon healing. Essential for ghoul healing build, but I can't see it incorporated into many other builds.

Rift Blade: creates a rift that deals damage when you attack them. Can be used, not super strong. Not advised.

Put Pocket: plant a bomb when attacking enemies. All bombs explode after a little while, dealing damage. If you wanna have fun, go for it. Not strnog though.

Mercury Heart: negates two damage instances after you defeat a dark enemy. If you're able to avoid damage in normal rooms, you can go into boss fights with a bunch of hearts and fight like you're invincible. Otherwise not very strong; you might get hit right after the hearts.

Big Mountain Pressure: boosts physical/magical damage every second. The boost is signifiant, but all effects are reversed after you attack an enemy. It's too slow for my liking, and the fact that you have to wait before you attack again to maximize damage is just...not my style.

Predicted Pain: dealing skill damage to the same enemy increases your damage. Can be quite useful for boss fights.

Go-getter: damage from items are boosted. If you're doing an item-oriented build, go for it.

Silent Cries: decreases skill cooldown for the other skill when you use one. Pretty practical, but doesn't boost damage directly. If your skills cooldown fast, then there's no need to choose.

Relapse: has a chance to re-inflict a status after it's canceled. If you're doing freeze/stun oriented runs, you can potentially control the boss forever. It's still a chance though, so it's really up to you if you want to take it or not.

Cursed dark abiltiies appear as red/black icons and two are offered in between the chapters. All of them have a positive effect along with a negative effect, so it's up to you to see if it's worth it. Given the sheer amount of them, I will pick out some of the good ones and recommend them here.

Shyness: if you're getting this right before the final boss fight, lucky you. Boosts damage if you're facing only one enemy, but with two or more, their attack power increases. Ideal for single boss fights; do not pick for normal rooms.

Aging: increases skill cooldown drastically in return for 15% less skill damage. If you have some other way to reverse that (e.g. soul strike), then a 120% in cooldown speed should be more than worth it.

Bone Shield: spend bone fragments to megate received damage. If you have a bunch of unspent boens and got this skill right before the final boss fights, you can probably win any level. After all, 50 bone fragments means 150 points of damage negated (at a 1:3 rate). You might not want to choose it early on, though.

Ambition: gain effects for the amount of core quartz (the currency for dark abilities) you have. This means that you will have to stash up. If you're doing high mirror levels, this can be quite useful as much more dark enemies appear than in lower levels.

Spirit of Negotiator: your first few rerolls are free at the black market, but each time you do it prices will increase. Can be qutie useful for buying items and being able to reroll for free. Remember to switch it out for something else later on though.

Life Change: at max, grants 300% increase in physical/nagical damage. All the healing orbs and potions you get from enemies and chests will not heal you (only the meal at black market and the Achievement ability). If you're confident in your skills, go for it.

Glass Body: you're invincible for a second after getting hit, which can be quite useful to avoid boss combos or numerous damage sources at once. Also amplifies your outgoing damage by 35% (at the cost of receiving 35% more damage). I don't really see much that's bad about it unless you're that bad at the game; amplified 35% damage and invincibility for 1 second every time you're hit is quite strong.

Other ones like Reversed Fate (which reverses physical and magical damage) and afflicition-based-ones (affecting freeze, bleed, stun, etc.) afre all situational. Based on your build/run/situation, decide for yourself what might be the best for your build.

Quintessence choices can vary quite from what you would choose in a normal run. In the Dark Mirror, you should either focus on dealing damage or avoiding damage. Thus, quintessences that straight up deal damage (Suonisio, Shadow Knights) aren't as strong as they are in normal gameplay due to the high hit points enemies have. Rather, focus on boosting your damage and avoiding them.


Succubus: Summon succubus, who swings a scythe over quite a wide area. Enemies who are hit by it are "charmed" for a few seconds, and in that state, they cannot deal damage to you. This can be very useful for boss fights if they are about to use a wide-area/high-damaging attack. It basically gives you three seconds of invincibility.

Slime: One of the strongest quintessences for this mode. Quite useless for normal runs, but here, three seconds of invincibility...that's no joke. That can get you out of a lot of sticky situations, and given its much faster cooldown than Succubus (15 seconds as opposed to 42), it's a certified life-saver.

Orc: If you're doing physical damage, Orc can help you reach ridiculous numbers: it doubles your physical damage (the number you see on your character information sheet) for a few seconds, but during that time, you take double damage. Use at your own risk. Yes, you can one shot bosses, but if you take damage, especially if you have a few omen inscriptions...well, no one can save you then.

Troll: turns all your attacks into critical hits for a while. Extremely strong for boosting damage, especially if you have something like Veiled Mask. Also strong if you have lots of bits of damage (e.g. Alchemist's "Unstable Summoning" skill, Ninja's "Shadow Clone", Joker's "Highlight", etc.). Pair with items and skills that boost critical damage.

Wisp: resets all your skill cooldowns and rotations. Being able to use your rotation and skills immediately again is certainly helpful, but the power of it depends. If you rely heavily on skills and/or have long skill cooldowns, it's worth considering. If you already have fast rotation and/or skill cooldowns or doesn't rely on skills very much, it might not be worth it. Personally, I rarely use it. It's lackluster compared to Orc or Troll in terms of boosting damage.

Any quintessence with a very short cooldown (less than 10 seconds) with the dark ability "Supernatural": The ability "Supernatural" boosts all of your damage sources by 40% when you use a quintessence, but for compensation you can't damage your enemies with quintessence. This menas that if you have something that has a very short cooldown, you can have an almost constant 40% damage boost. So, if you choose this ability, avoid quintessences that mainly deal damage and/or have long cooldowns.

Cyclops: it can be a decent pick since it gives 20 shields, which helps a little with survivability. It works well with the shield build (see "Builds").

Face Bug: The "common" rarity is certainly a mystery here. You throw a bug onto an enemy, which then allows you to deal extra 30% damage to them. A solid damage boost, quite strong for boss fights. Imagine you're fighting a skeleton and they throw a bug onto your face. I'm surprised it doesn't have stun + weakenedl; should be a legendary quintessence (lol).


Balrog: turns you into a demon of hellfire for a duration. Yes, it sounds cool and looks flashy, but its lackluster damage combined its forced, altered movements (extremely long dash, skills) makes it rather dangerous to use. You are going to want to position yourself carefully to avoid damage here, and Balrog forces you to move around if you want to maximize its damage. While you can use it to some fruition, it's overall too dangerous and just not as effective or flexible as something else.

Imp: A weak quintessence in general. Not much to say. The imps run around freely, which is partly the problem. You can't really control them, which means that they are going to miss out a lot of damage and do some unnecessary damage. They don't exactly deal high damage either. It's just overall bad. Don't understand why anyone would pick it,

Harpy: Delete this quintessence, please.

Most other quintessences other than the mentioned "recommended ones". Ones that do direct damage (e.g. Ifrit, Flame Dragon, Raven Lord) are hardly significant in harder fights, while ones with special effects (e.g. Banshee, Naias) are weak in comparison to some of the others. Actually, a few can be used here: Lyweasel boosts your dash distance which can be useful; Ogre reduces damage taken by half when you stand near it, and Spectre gives you a very brief invincibility. Still, they fade in comparison to three seconds of invincibility from the slime or doubled physical damage.

As mentioned above, through the countless items and inscriptions you can pair with, there are some natural builds and synergies that are strong, especially in the dark mirror levels.

Here's a rundown of some of the main/strong builds:



Sack up your attack power and deal damage through your skulls. Aim for items mentioned above in "items", many of which provide direct damage boosts. A successful damage-stacking run can usually get physical/magical damage to about 1000% and more. For example:




Choose strong, solid damage-dealers who can reliably dish out attacks. Alchemist, Bomber, Berserker, Ghoul, Samurai, Living Armor, etc. For dark abilities, choose ones that can boost your damage: Predicted Pain (which amplifies skill damage to the same enemy), Collection Desire (if you have many inscriptions), Soul Strike (which amplifies skill damage), etc. If you choose this build, you're either very confident of your luck or your skills. If you're lucky enough and stack up to insane amounts of damage, you can one-shot everything. Or, if you're skilled, you can dodge all the enemy attacks and dish out fat damage at the same time. To play, it's recommended that your familiarize yourself with all the enemy and boss attacks (see "Enemies" and "Bosses").



Choose Ghoul as your main skull. You don't really nede another skull; early on, destroy the skulls you see and level ghoul up as soon as possible. The build focuses heavily on the inscriptions Revenge and Relic; Revenge allows you to heal damage taken by damaging the enemy while relic provides additional healing along with proportional true damage. It's recommended to get relic to 4, and for revenge, 2 is enough. Items like rejuvenating root (which heals you a little bit when you're hit), Passed-Down Scabbard (which summons additional attacks when you heal), the Chosen Cleric's Bible (which boosts your magical/physical attack and deals damage to nearby enemies ever two seconds) are all crucial to the build. The dark skills "Piety" (which increases HP restoration) and "Reckless Posture" (which grants taken damage reduction and attack damage increase when you're hit) are also essential.
The idea is that with 30% increase in HP restoration (from Piety), the HP you restore from revenge almost makes up for the damage you take, if not exceeding it. This means that while you have to dodge, if you're actually hit, simply attack the enemy and you'll be able to restore the lost HP. However, due to revenge's cooldown and delay, the ghoul skull provides secondary HP restoration with its meat chunks mechanic (after it's upgraded). When you have 5 or more meat chunks, you will be able to restore a portion of HP when you lose them, and paired with Piety, you can restore ridiculous amounts of health. Do note that when you swap, all meat chunks are lost, so it's a good idea to stick with Ghoul for the entire run.






Nothing is more satisfactory than seeing your little army of spirits fire at the enemies, huh? The fairy tale inscription requires five to unleash its full power, but you'll be rewarded if you manage to do it (a huge, buff spirit king called Oberon that do all kinds of cools things like shoot orbs and lasers).
It's a good idea to keep Shadow Spirit with you from the beginning, because if you run into Light Spirit, it'll transform your Shadow Spirit to Shade. Lake In A Bottle and Water Spirit Undine (from the DLC) also transform when paired together and grants you 110% increase in magical attack, so they're very strong together. If you can get Elementalist's Blessing (which boosts magical damage for every spirit you have), take it. You can also take the Omen: Desair if you want, which is the dark mirror's special spirit that functions similarly to Dark Spirit Shade but also changes the appearance and some of the attacks of King Oberon.
Basically, stack up a few spirits and summon King Oberon, while at the same time making sure you have a decent magic damage stat. It's pretty simple: you focus on dodging and leave the dirty work to your spirits. It might not be the strongest build, but it's certainly fun. Plus, after the inscription gets modified by the witch (after you beat the final required boss), King Oberon transforms into his "true" form, where he is less buff but a lot more white and powerful (he has an attack where he shoots lasers all over the screen. Looks cool af).
You can choose the "Go-getter" dark ability, which is unlocked later. It boosts damage dealt by your items, which will directly boost your spirits' damage.

This build focuses on bleed/poison physical damage. Choose Skeleton - Sword and another skull of your choice. Skeleton - Sword's skills and attacks all have abilities to cause wound, which will then turn into bleeding if wounded again. Bleeding causes a single large burst of physical damage, and once upgraded to legendary, applying bleeding again will cause the enemy to develop a "tetanus", which is poison damage that ticks three times/second and continues for three seconds.
As for items, focus on maximizing that damage. For bleeding: Blood-drinking sword (which increases physical damage and critical rate if you cause bleeding), Terrible Blade Shards (which allows you to summon extra attacks when you cause bleeding), Miracle Grail (which amplifies bleed damage greatly every once in a while), et cetera. For poison: Approaching Death (which amplifies poison damage), Chimera's Poison Fang (which kills poisoned enemies sooner), Stone of Plague (which increases physical damage when you deal poison damage), et cetera. You can also use Disposable Syringe (which inflicts poison when you deal a critical hit) with the quintessence Troll (which turns all attacks into critical hits for a while). It depends on which type of damage you want to do; for me personally, I prefer bleeding over poison because it's quicker and deals more damage. Whatever you're aiming for, make sure to max out the corresponding inscription (Excessive Bleeding/Poisoining) as they help greatly. As for dark abilities, there are two cursed ones that are specifically designed for poison/bleed: Terminal Illness (increases poison duration, decreases damage) and Bloodfest (deal bleeding immediately when wouding an enemy, but at a lower damage). It's up to you to choose whether you need it or not (Bloodfest combined with Skeleton - Sword's swap skill is quite deadly). You can also consider the ability Relapse, which has a chance to re-inflict status ailments after it's cancelled.
Basically, use skills and attacks to deal damage. Skeleton - Sword's attacks have a chance of automatically dealing wound, which can then turn into bleed, and its skills can also cause wound. Use skills and attacks alternatively and rely on the bleed/poison damamge to kill the enemies.



For skull, choose Skeleton - Shield and another skull of your choice. This build revolves around the key item Symbol of Toughness, which initiates a counterattack shockwave when you receive damage with an HP shield. It's best to have two of Symbol of Toughness (through the slime npc). Basically, you try to stack up as much shield as you can and deal damage through the shockwave. Architect's Breastplate (which grants momentary shields), Dark Priest Robe (which grants HP barriers when your HP falls below a threshold), The Chosen Warrior's Armor (which grants shields when you enter a map), et cetera. Dark abiltiies like Coziness (which boosts cooldown speed and critical rate when you have a shield), Hard Shell (which grants shields when you enter a map) and Go-getter (which boosts item damage) are all crucial.Choose the Cyclops quintessence, which grants 20 shields when you use it. All of this combined should give you quite an impressive amount of shields, which then allows you to even one-shot bosses with the counterattack damage. Quite an easy build to play; very tanky and fun.



Now, there are many ways to go with the basic attack build. Basically, you increase your attack speed and then spam the attack button. Add other effects/combos to your basic attack with items like Golden Mane Rapier (every 3rd hit conjures a blade rift), Evil Sword: Kirion (additional attack), Afterimage (extra attack, magical), Mana Gauntlets (increase magical damage through basic attacks and creates additional shockwaves), Pain & Despair (increase attack speed), Omen: Soul Killer (additional attack), et cetera. Inscriptions like Rapidity and Hidden Blade are all viable.
Many skulls have strong attacks, and you are free to choose whichever that works well. Viking creates thunder when attacking, which is quite strong combined with Storm Clouds (item that conjures lightning). Clown's attack explodes with extra damage every few hits, and when Gene is upgraded to legendary, every third hit conjures three shadows for attack. Water skull can gain splashes faster with faster attacks, and the Dominator has a second form where his attacks are enhanced and deals combo damage. Et cetera.
Many dark abilities fit with this build. Innate Power (which boosts normal attack damage), Lethal Speed (which boosts attack speed when dealing a critical hit), Weakness Exposure (every third attack deals extra damage), Electric Field (which creates a field after 7 basic attacks), Rift Blade (which deals extra damage when attacking an enemy), Contract of Death (which boosts normal attack damage), Cracked Tongue (boosts basic attack and decreases skill damage), et cetera, et cetera.

Disclaimer: This guide is born out of entirely personal experiences. From a total of 400+ hours (across multiple accounts), I am confident that I have developed a somewhat good understanding of the various mechanics of the game and the dark mirror mode. Thus, this guide is a list of recommendations/tips that I have gathered throughout countless runs and hours of experience. Undoubtedly, people will have different opinions/preferences. Try all of them out yourself and develop your own opinions (that's the fun of the game, after all). The aim of this guide is to help people who may be struggling with the dark mirror levels to potentially help them progress faster, or enjoy a different experience. It can also help with one's understanding of the game if they're unexperienced. Still, take everything with a grain of salt (except the skull recommendations; trust me, the ones I recommend are the good ones). Nonetheless, have fun! Skul is the ultimate journey of discovering, learning, and eventually mastering the hundreds of different items and skulls the game has to offer. The journey is a most memorable one, and it's one to be enjoyed thoroughly.