Wanting some achievements that you don't have, but don't know how to get them? Look no further, this guide should help! Be aware that this guide contains spoilers.

Good luck and happy hunting!! ♡


Creds to DarkSlayer's amazing art

The Legend Begins
Return to the castle after dying - you'll simply get it by dying on your first run


Go Home
Rescue the demon King - beat the game! Press 'continue' after credits roll


You get these achievements simply by progressing through the game and beating the boss of each area.


Rescued Elder Ent
Defeat Yggrasil, the first boss


The End of the Gold Mane Knights
Defeat the Leiana Sisters, the second boss


False Goddess, Disappear
Defeat Chimaera, the third boss


The Fall of the Leonia Order
Defeat St. Joan II, the fourth boss


The Final Battle of the First Hero
Defeat the First Hero, the fifth boss

What Should I Buy
Spend 1 minute in the Black Market


Brain at Full Throttle
Spend 5 minutes in the Black Market


Too Much of a Talker
Simply keep talking to Headless until you unlock the achievement

Inventory Management
Re-stock continuesly - refresh the item shop until you get it. I've heard people needing anywhere between 5-10 refreshes. I got it after 5 refreshes

All the following achievements are related to renovation of the Demon King's Castle. You will need to rescue the Death Knight on the 4th level to make him appear in the Castle. He'll let you purchase renovation services (cosmetic) in exchange for dark quartz.


Castle Restoration Plans
Fully restore the Demon King's Castle - costs a total of 127 500 dark quartz


Rules of Etiquette
Simply jump on top of the throne to the left in the Castle, around here [imgur.com].

The Dwarven Chandelier
Jump on top of any chandelier in the castle, for example like this! [imgur.com]
This requires buying upgrades from the Death Knight!

You get the following achievements by beating all the bosses in the game without being hit a single time. I recommend looking up guides on how to do the different boss battles.


Quick Movements
Defeat Yggdrasil, the first boss, without taking damage


Master of Speed
Defeat the Leiana sisters, the second boss, without taking damage


Deadly Power
Defeat Chimaera, the third boss, without taking damage


The Levitator
Defeat St. Joan II, the fourth boss, without taking damage


The God of Battle
Defeat the First Hero, the fifth boss, without taking damage


The Strongest
Defeat the First Hero in the Dark Mirror without taking damage

A bunch of achievements I couldn't fit into any of the other categories..

Rookies Welcome
Play on rookie mode - turn it on in settings. You can turn it off after getting the achievement if you don't want to play with it activated!

Cold-Blooded
Do a run where you don't free any captive NPCs. It's fine to break the NPC cages as long as you don't interact with them afterwards!


Focus
Die by taking damage from a trap


The Hero Killer
Kill 100 heroes (mini-bosses). You fight one in 1-2, two in 2-2, three in 3-2 and one empowered hero in 4-2. If you manage to kill all possible heroes (7) in a single run, you'll need a total of 15 runs

The Skeleton King
Defeat the First Hero only using Little Bone. I used a powerful skull for phase 1 and 2, then swapped in Little Bone to deal the last hit[imgur.com] during phase 3

You get all of these achievements by maximizing the evolution of your Skull. How many bones you need to get it to legendary (max) depends on the rarity of the original skull.
There are a total of 36 skulls that are able to evolve. In addition there are 7 legendary skulls!

Keep in mind that you have to buy three of the Skulls from the merchant Grave Robber[imgur.com] at the Black Market! He's in the top left and also sells new equipment/quintessences. The skulls he sells are: Stone Monkey, Grave Digger and Davy Jones!


COMMON SKULLS

War Fanatic
Acquire Carleon Commander - upgrade the Carleon Recruit to max


Guardian of Nature
Acquire Elder Ent Skull - upgrade the Ent Skull to max


All Soul's Day
Acquire the Savior - upgrade the Grave Digger to max


White Mage
Acquire Sage - upgrade the Mage to max


The Back Alley King
Acquire Desperado - upgrade the Petty Thief to max


Charge! Again! And Again!
Acquire Vanguard Captain - upgrade the Skeleton-Pike to max


The Best Offense is Defense
Acquire Guard Captain - upgrade the Skeleton-Shield to max


An Honorable Name
Acquire Royal Guard Captain - upgrade the Skeleton-Sword to max


Ghostly Elusiveness
Acquire the Overlord - upgrade the Stone Monkey to max


The Greatest Werewolf
Acquire Eternal Werewolf - upgrade the Werewolf to max


RARE SKULLS

An Endless Appetite for Research
Acquire Dark Alchemist - upgrade the Alchemist to max


Start the Show
Acquire Joker - upgrade the Clown to max


The Embodiment of Cold
Acquire Frozen Spirit - upgrade the Frost Skull to max


Demon King Castle Gargoyle
Acquire Golden Gargoyle - upgrade the Gargoyle to max


Praise Me!
Acquire Spirit - upgrade the Gene to max


Dominating Size
Acquire Ghoooooul - upgrade the Ghoul to max


Ultimate Weapon: Bow
Acquire Sniper - upgrade the Hunter to max


The King of the Labyrinth Ruins
Acquire Minotaurus III - upgrade the Minotaurus to max


Arms Expert
Acquire Eternal Mummy - upgrade the Mummy to max


Rider Instincts
Acquire Nightmare - upgrade the Rider to max


Explosions are a Work of Art
Acquire Demolitions Expert - upgrade the Skeleton-Bomber to max


Too Big to Be Called a Sword
Acquire Warlord - upgrade the Warrior to max


The Raging Wave
Acquire Poseidon - upgrade the Water Skull to max


UNIQUE SKULLS

The Unbreakable Pact
Acquire Devil Berserker - upgrade the Berserker to max


The Dark-Armored Knight
Acquire Dark Avenge - upgrade the Dark Paladin to max


From the Deep Abyss
Acquire Abyssal Monarch - upgrade the Great Warlock to max


Burning Soul
Acquire Soul Knight - upgrade the Living Armor to max


The Legendary Ninja
Acquire Master Ninja - upgrade the Ninja to max


Destructive Instincts
Acquire Destroyer - upgrade the Predator to max


Beheaded
Acquire the King - upgrade the Prisoner to max


A Stylish Entrance
Acquire Super Rock Star - upgrade the Rock Star to max


The Final Mystery of the Arts
Acquire Neo Samurai - upgrade the Samurai to max


LEGENDARY SKULLS - achievement unlocks immediately

Sealed Power
Acquire Archlich


The Legend of the Arena
Acquire Champion


Do you fear death?
Acquire Davy Jones


Wanna Play a Game With Me?
Acquire Gambler


The Ruler of the Nether World
Acquire Grim Reaper


The Dokkaebi’s Supernatural Stomp
Acquire Yaksha


Say My Name
Acquire the Dominator

You unlock these new skulls by entering the Hall of Gods through the green trapdoors[imgur.com]. They'll be available for future runs once you've tried them. Keep in mind you have to try all evolvable skulls before you can unlock the legandary one! It'll look like this once it available: https://imgur.com/a/3krXcrn

COMMON SKULLS

God of Thunder
Acquire Thundergod - upgrade the Viking to max


For Tonight, We Dine in Hell!
Acquire Demi-God - upgrade the Slave to max

RARE SKULLS

Strength of 10,000 Men
Acquire God of War - upgrade the Officer to max

UNIQUE SKULLS

Hero of the Night Sky
Acquire the Absolute - upgrade the Ascetic to max

LEGENDARY SKULLS

Sword of Promised Victory
Acquire Unknown King

Dark mirror content unlocks after beating the First Hero for the first time!

PROGRESSION

Dark Side of Harmonia
Enter the Dark Mirror to arrive in the Dark Side of Harmonia


New Start
Return after dying in the Dark Mirror - you'll get it after ending your first run


Broken World
First Dark Mirror Destroyed - simply complete your first successful run (level 0)


A Worthwhile Adventure
Level 1 Dark Mirror Destroyed


Courageous Act
Level 2 Dark Mirror Destroyed


Result of your Efforts
Level 3 Dark Mirror Destroyed


Self-Confidence
Level 4 Dark Mirror Destroyed


Energy and Perseverance
Level 5 Dark Mirror Destroyed


Spirit of Challenge
Level 6 Dark Mirror Destroyed


Surprising Move
Level 7 Dark Mirror Destroyed


Phenomenal Success
Level 8 Dark Mirror Destroyed


Great Achievement
Level 9 Dark Mirror Destroyed


Nothing is Impossible
Level 10 Dark Mirror Destroyed


BLACK MARKET
Special Guest
Once you reach level 3 the Collector merchant will sell an additional item. It's located above the refresh button[imgur.com]. Buy it!

All-In
Starting at level 6 you can restock a new item pedestal [imgur.com]. Restock until it hits 0! Each restock costs 500, so it'll cost you a total of 10 000 Dark Quartz to get it. Save up before going for this

Solid Career Choice
Once you reach level 7 you can buy extra inscriptions. You see them[imgur.com] as soon as you enter the Black Market. Buy any inscription on both of them to get the achievement


ABILITIES
Best Condition
During runs, the old man by the bonfire will let you buy dark abilities. Equip four different ones at the same time to unlock the achievement. It doesn't matter if they are red or purple!

Dark Ability
Acquire all dark abilities - you unlock this automatically at level 10. You get more dark abilities at level 4+8 and then the final cursed abilities once you reach level 10. No need to buy/use them all

The Cursed
Have 4 cursed dark abilities at the same time - instead of equipping regular dark abilities (purple) equip the cursed (red) ones[imgur.com]


INSCRIPTIONS
Hate the Sinner, Love the Sin
Have the 'Sin' inscription - rescue the Evil druid during a run and he'll drop an item[imgur.com] with the "sin" inscription

Terrible Omen
Have the 'Omen' inscription - once you get to level 2 Dark Mirror there will be cursed chests that drop items[imgur.com] with the "omen" inscription


SPECIAL
Spider God's Protection
Once you reach level 5 - choose one of the three boosts Arachne offers and level it up to 10[imgur.com] during a single run. It costs a total of 150 bones!


Heart of Darkness
Acquire 100 Dark Quartz Hearts. You get these hearts by killing the purple mobs

Content is available in the Dark Mirror and acts as an ending to the main story! Keep in mind the DLC is bought separately from the game

PROGRESSION

Hall of Gods
Arrive at the Hall of Gods - enter through the green trapdoor[imgur.com] for the first time!

The War Begins
Reach chapter 6 for the first time - beat the First Hero and go through the portal[imgur.com]


True Peace
Defeat Alexander, the Emperor of Carleon at the end of chapter 6


ALTERNATIVE ENDING
Note that you have to collect all six enriched quartz during a single run to unlock this secret boss fight against Dark Skeleton Skul! Once you've collected them all during a run you won't have to do it again, though the secret locations will still be accessible. I have a link to screenshots of all locations below:

Hidden Existence
Find Enriched Dark Quartz - collectibles with hidden locations [imgur.com]

Dark-Tech Tank
Encounter the mysterious being - unlocked once you walk into the boss room with Dark Skul


True Salvation
Defeat Skul, the Dark Skeleton - beat the boss!


SPECIAL
Witch's Help
Modify 5 different Inscriptions - you'll be able to modify a single maxed out inscription before the final boss

The Power of Science
Use the Dwarf Engineer's high speed transportation system - available at the start of ch. 6 the second time you go there to skip directly to the Demon Castle

Bone Specialist
Acquire Skul's Fragment 3 times - after beating Dark Skul you can choose 1 fragment from a total of 9 items[imgur.com]. Meaning you gotta beat him 3 times!

This is the updated achievement list as of patch 1.8.0!
Hopefully this was a helpful collection of information for some of you. Once again - happy hunting to you all!