First of all, I haven't thoroughly investigated the game, so there might have a couple of things that could be improved. If you find so, feel free to make your own guide.

Second : sorry for new players, the game is really different between early game and mid/late game that I cannot help you. Luckily there are a lot of useful information in this guide. If anyone could make an early game guide, the community would gladly appreciate it.

Of course, you all know that the goal is to beat Tier 20 boss.
But beating the boss is always easy. No. the hardest part is to beat the Lunatic mission.

Those missions are always hard because you have red mobs, and those red mobs hit from far away. Thus you need enough HP in your base to sustain the damages.

However, if you want to increase your HP, you will need to increase your gold cap. And that is the longest part.

This guide will explain the mechanism (or part of it) behind HP, gold cap, and a couple of others things.

At first, you need those Aether upgrades:

• Diabolus March
  
  Once you kill monsters really fast, you want monsters to spawn faster.
  
• Dowsing Rod
  
  In chests, you wil find traps. Soon you will be flooded by traps, but in the beginning, it's really useful.
  
• Monster Laboratory
  

This upgrade is really useful it increases the number of monster you trap with one trap (I.E. you use one trap, you capture 1000 monsters at max level), but you don't need to max it ASAP. It will help you to finish the Daily Quests really fast.


You will anyway have to max all others upgrades (except Perpetual Mobility... which is way too expensive), so I will explain as much as I can their purpose.

Improvement:

Improvement are unlocked by your level (2110 on my screenshot). Lvl2000 unlocks "Gold Cap", Lvl2010 unlocks "Gold Gain", Lvl2020 unlocks "Exp Gain", Lvl2030 "Boost Power", Lvl2040 "Density", and Lvl2050 "Spirit Power". It always works with the same cap levels: x00, x10, x20, x30, x40 and x50.
Based on how many spirit I place on an upgrade, I gain a tiny bit of something every tic. For instance, as written at the bottom right of the screen I gain 2.01e17/sec Gold Cap, and the current total bonus provided by Improvement Tier 20 Gold Cap is 2.77e30 (it means that on the sheet Tier 19 it will provide a different bonus, and you have to sum up all the Gold Cap bonuses of all sheets to have the total amount given by Improvement)
Whenever you level by one any of those upgrades, you gain 1 in the "improvement milestone". Here I need 40 more levels to reach the next milestone. This milestone will multiply the bonus of all upgrades (the 2.01e17/sec Gold Cap will be increased)

• 
  I assume it provides free 1000 levels to any upgrade.
  
  
• 
  This upgrade improves the number of "improvement level" (the multiplier is increased). It's not really useful at start, but is really really useful at the end (with equipment)

Crafts:

In order to craft, you need resources (first line top left). You need white squares for white crafts, yellow squares for yellow crafts, etc etc. Those squares are obtained by doing missions.
To craft Arrow Tier 20, you need Arrow Tier 19, etc etc. When you craft an arrow, it will have a quality. Once it reaches quality 100, you can place it on the corresponding floor. Note that the effect varies whether you are in a challenge or a mission.

• 
  
  Increase the quality of a craft. Ie : less resources needed to reach quality 100, and also faster to reach quality 100.
  
• 
  Self explanatory : increases the speed to craft.

Skill:

Skills can be auto casted by a left click on the skill. Sometimes, it is better to cast it manually. "Unlock All Blocks" for instance, is great to keep and use only on the hardest level of a mission.
Every time you cast a skill, it increases its counter (total activated). This boosts the passive effect. Gold Cap for instance, has a passive boost + an active boosts while the skill is active (double bonus). It is limited to a cap of 20 per... rebirth? ascension...? I don't remember which one.

• 
  Keep a part of the passive bonus after a rebirth or reincarnation. Keep all the bonus if maxed
  
• 
  Increase the maximum of total activation, hence the passive boost.

Equipment:

Equipment is really useful, but it's a chore to change.
There are 49 slots per sheet, and 4 sheets available. Some slots can be purchased ingame, some with Epic coins, some with upgrades. The equipment with letter E are equipped ; the equipment surrounded by yellow square are kept after a rebirth.

• 
  Will increase the number of yellow square on the first page. Note that it is pointless to max this skill, it's too expensive.
  
• 
  Self explanatory: increase the amount of slot for equipment
  
• 
  Self explanatory : increase the amount of equipment you can equip.

Expedition:
(see the inventory screenshot)
Based on the monsters you have caught and used in your base, you can start expeditions. It will provide chests which contain equipment and Ascension Spirit (red).
You need food to start expedition. You get food by killing monsters. On the screenshot, I have 2.6B food.
You need keys to open chest. They are in the chests (!) of monsters.
When you destroy equipment, you obtain yellow, blue, red orbs (component? parts? scraps?). They are used for artifacts.

• 
  Whenever you use nitro, your expedition will be boosted. Since you will ALWAYS use nitro... it's mandatory at a certain point.
  
• 
  Self explanatory: increase your chance to have equipment within a chest.

Artefact:

Artifact gives really nice bonuses. Best is of course Gold Cap and Expedition Chest. Move your mouse on any artifact to see the formula. You will learn that at lvl101, I would gain 54 chests instead of 27 (the formula is not visible on the screenshot - but you can see that every expedition provides me with 27 chests))
Price of artifact is doubled (in term of "orbs" needed) every purchase.
Note that the "damage bonus against XXX" is useless IMHO, since you kill everything with your equipment.

• 
  I consider this upgrade as expensive and not that useful in the mid game. It is however MANDATORY in the endgame.

Ascension - Improvement:

Pay attention that Ascension has multiple sheets.
Every x sec (7.587 sec on screenshot), you increase the bonus to EXP Craft. I assume (haven't checked) it both for Challenge and mission).

• 
  Self explanatory : any bonus earned will be kept after rebirth.

Ascension formation:

You can increase the level of a boost by buying the corresponding boost. However, you have to select which boost is activated or not by checking the corresponding checkbox. Here, the Boost power is activated and another one not visible, and you can see that the amount of Ascension Spirit (red) is the half of the total I possess: I have 714.11K Ascension Spirit (red), and half on each skill (356.0K) per checked skill.
NOTE: do not increase Boos Power skill level, it could go wrong.

• 
  All levels are boosted by this skill. It's a bit hard to check on the above screenshot (I press on alt+Print Screen, and Alt indicates what would be the next upgrade by buying with all my money), but I leveled once the Boost Power. The current upgrade is 1001, which is written as lv1.00K => the current level is 1000 (my Aether bonus) + 1 (the level I bought)

Ascension Breakdowns

This display various information. The most important one is... Bonus Gold Cap/Gain/Exp Gain. It is really important to notice that Gold Cap is increased by the number of time you have ascended.

• 
  I haven't checked, but I assume this bonus belongs to Ascension Breakdown.

Now you know a bit better all the Aether upgrades, we can talk about the strategy to kill Tier 20 boss.

Beside HP and Gold Cap goal, you will have to make the max Aether and Anima farm. Once you have maxed all the rebirth stuffs, you will have no reason to rebirth. It will be a really really long last run. The reincarnation breakdown is not that great in term of HP and Gold Cap.

It means that your strategy will be to rebirth often, and to reach as far as you can, without any need to push. Don't forget to complete as much quests as you can between rebirth, as it resets and give Aether.

The first thing to focus on is getting those 4 pieces of equipment:

You need 3 of those (maybe 4? Probably linked to Doppleganger: few dopple, more swords)
It can insta kill any monster (including boss). With 3 of those, you can complete any mission without any issue... except for Lunatic ones...

You need one pendant. It will help you to be full of Nitro all the time. It means monsters will be killed faster, will spawn faster, and expedition will finish faster. (with the right Aether Upgrades...)

For Lunatic mission, you will need a specific setup:
1) Layout:

Fill your screen with EXP craft and Gold Craft. All your sheets have to be filled with the same pattern for Quality, Color and Lineage bonuses.

2) Equipment:


I don't know which one of those two is the best. Maybe a combination of the two.
Anyway, pay attention to the bonuses (option effect): you must pick in priority Challenge Imp. [Base Level] OR Challenge Imp. [Defense]. Rest is useless.

3) Ascension Formation:
Based on the HP of your base, either:

• All in Challenge Base HP
  
• Half in Challenge Base HP, half in Boost Power.

Challenge Base HP must be bought as high as you can.
You will Half/half if you have enough HP and your game will play without you.
If it is too short, you will need to stop the NItro, and use trap on all mobs you will see, with highest prio on red ones.

4) Full Health skill must be set to OFF: you have to activate it manually when needed (around 1000 mobs killed)

5) All your base are belongs to us:

In Training, you must set as many mobs as you can (here you cannot see, but it's 1M).
In Research, you must set as many mobs as you can (here you cannot see, but it's 1M)
In Improvement, you must set as many mobs as you can. Here it's 1M.
As far as I remember, Training will provide XP per second, so you must increase its level by killing mobs (Nine Tale for Nine Tale).
Research is REALLY useful to catch more often red mobs when you need to finish a Lunatic mission.

Ok, so now the most important part: if you want to complete Tier 20 Lunatic, you need 2e92 gold cap, in order to buy EXP craft on floor 20. But in order to reach 2e92 Gold Cap, you need a LOT of equipment. Which mean you cannot rebirth or you will lose useful equipment...

So here is the most important sheet: statistics.

How does it work?
Just a reminder of mathematics:
If you have A * B * C * D * E = 1e50, then if you double any of your bonus (for instance: (2*A) * B * C * D * E), you will have 2e50. It's great, but if you aim at 2e92, you're still really far, while you doubled your bonus. Keep that in mind, I will use it soon.

Gold cap is a base ("Additive Total") multiplied by all of others bonuses.
Additive total is the sum of Base (5) + Improvement (9e30) + Ascension Formation : +0.
Ascension Formation is "Initial Gold Cap" first raw. I tried to level it, it's useless.
Mathematics reminder: 1 000 000 + 9e30 = 9e30. 1 million is so small that it's invisible in the sum. It's not even 0.000001%.
=> Improvement Gold Cap is THE thing you have to increase, the two others are useless.

Regarding the multiplicative, since it's multiplicative, we have to see each raw and max it.

• Base: Cannot be increased
  
• Mission Milestone: The more mission you complete, the better it is. However... it's a constant since there is no mission Tier 21.
  
• Challenge Milestone: Same as above, it's a constant.
  
• Challenge Bonus: It is based on the sum of all Bosses mission infinite play. You have to farm for all of them. And the nine tales ones are really long.
  
• Ascension Formation: This bonus is increased by the level bought + the number of Ascension Spirit (red). The formula is [Level] * [Ascension Spirit] (roughly) => with the mathematical reminder, if you want to double this value, you have to double your amount of ascension spirit... or the level... guess how long it takes to increase your amount of Ascension Spirit... 700K... I bought for more than 800K Ascension Spirit of upgrades in the Ascension Store.
  
• Ascension Bonus: based on the number of ascension performed during this rebirth: 50.09K ascension. If you want to double this bonus, you have to double your number of ascension...
  
• Ascension Store : it's a constant.
  
• Active Skill Passive: it's a constant.
  
• Equipment:
  You need to keep those armors with the best bonuses. I haven't found any [lvl9]*3...
  
• Artefact: Once again, the price double every time you increase the rank. And the effect is doubled.The impact of level is not that great. I however reached rank 26 lvl205...
  
• IEH Bonus: I hope you played this game. The bonus is a constant, but is mandatory...

So once you want to reach your highest gold cap, equip only gold cap armors, use a layout full of gold gain, place you on the highest level with yellow gold gain (yellow gold gain Tier 19 > white gold gain Tier 20), use booster with no mob, and wait for the auto buy to buy everything.

You might have to do it multiple times because of the Improvement Gold Cap...
Regarding the improvement gold cap, you need to use 3 assassin swords (+1 locket) and... everything else will be

Note that there is usually a difference between an equipment R3 and an equipment R2 in the raw value of the equipment. But here, both the Scale ring and the shield provides a bonus of +42 (if i'm not mistaken). So it is better to have a shield with +42 and two imp.upgrade lvl whatever than a mere Scale ring +42 with only imp.upgrade lvl whatever.
With those equipments, kill as much as you can/want while grinding the Gold Cap Bonus.

But... the issue with the improvement is that you need to increase your level. In order to reach Improvement Gold Cap lvl21, you need to reach lvl2100. Which means that you need an xp equipment.


So let's recap : the equipment needed is :

• 3 Assasin swords
  
• 1 Chest Pendant
  
• 29 Enchanted Cloak
  
• 25 brilliant wing
  
• 25 Scale Ring
  
• 29 Scale Armor + Locket of Knowledge

And if you're willing to farm prior to that, 25 Holy Rings (to farm the Ascension Improvement bonus for Gold and Exp). Note that once you have farmed enough, the Holy Rings are useless.

The more I wrote, the more I noticed it spreads everywhere :D
I hope it is somehow clear.

As you can see, this game is NOT an idle game. It is a real active game. Furthermore knowing that you have to actively farm for expedition, and dismantle a heavy load of useless equipment (why is there not a single "dismantle everything but R3 equipment" button?)

If you read more than once this guide, you might understand 2/3 things really really helpful. The global strategy depend on how you play. Ideally you could rebirth every 2 days, but you have to be able to change of tier at every moment.

For the last run, start with rebirthing in loop, reaching the highest amount as you can. I was aiming at 100 000 rebirth, but I got bored at 50k...
Then reach Tier 20/21, then farm for infinite missions (first all for HP, then all for Gold Cap).
Then farm for XP to reach Tier 20 Exp gain.
Then farm for gold cap (always check how far you are from a useful craft)
Then farm again for XP to reach Tier 21 Gold Cap (lvl2100)
Then farm again for Gold Cap improvement (with scale ring).
Once you can buy Exp craft Tier 20, congrats (almost).
Then try to complete the Lunatic mission (you need something like 5.49e77 HP. Below it's way too tough)

Gl!