I got the idea for this guide while brainstorming different team combos while I was falling sleep.

Oh so much love to Mr. Dale Turner for making such a fun game, and shout out to Retromation whose Youtube series showed me the game.

I just want to write down some of the things that I've found as basic elements of strategy in thinking about the game.

The loading tooltip says that 1 point of defense equates to 1% more effective HP.

So we can think of effective HP as

(100 + Defense) / 100 x HP

e.g. Defense is a kind of percentage modifier of HP.

We can also surmise something like this:

At 0 Defense, a character takes 100% damage from an attack, i.e. an incoming attack of 100 deals 100 damage.

At 100 Defense, the character has 100% more effective HP and so should take half damage from the attack, i.e. 50 damage.

At 200 Defense, the character has 200% more effective HP and should take one third damage from the attack, i.e. 33 damage.

From this we can get this principle:

Defense has diminishing returns -- the first points of defense you add to a character are saving more hit points than the later points are.

If you're debating adding an HP item or a defense item to your tank, you can compare which adds more true Effective HP to decide at a glance which is better. Do you want 100 HP or 10 defense? If your current hit points are 1000, both add the same effective HP; if less than 1000, the HP is better at a glance, and vice versa.

HP / Defense interactions

This gets more complicated when we consider shielding, healing, and true damage.

Shields

Shields appear to count just like pre-emptive heals. Giving a character 200 shield is stronger the higher their defense is. However, shield is wasted when the character is not immediately under attack.

So the value of a given amount of shield scales with defense, but the amount of shield you get can scale with a lot of different things depending on the source. First things that come to mind are the Paladin, whose shield supply scales with his defense, and the Wildmage and Brawler whose scale with their HP.

Healing

Ordinarily in video games healing pairs very well with high defense, as each hit point healed counts for more when it's flowing into a tanky character.

However, in Astronarch, healing often scales with the recipient's max health. For example, the cleric's ability always heals 10% of the recipient's effective HP, so adding health and adding defense to the recipient can be equally effective -- what matters is maximizing effective HP to maximize the effectiveness of the heal.

There are exceptions -- the Bloodmage heals more depending only on his OWN max HP. The Warlock and Fiend heal more depending on their DAMAGE DONE, which is modified by both their attack and their targets' defense. Heals from a Warlock or Bloodmage are more valuable on high defense targets, not high Effective HP targets.

So you can start to think strategically about, depending on what your source of healing is, what kinds of sources of defense you want to rely on.

True damage

And of course bleeds, burns, poison, and piercing damage all ignore Defense as well as Shields. So a high-HP target is most naturally resilient to these.

I find that I will ALWAYS grab the Enchanter's Chainmail and give it one upgrade and keep it in my back pocket. There are enough fights in the game that you can completely hose down by having this item.

Short of that, you can try to prioritize paths that keep you away from Bleed-y, poison-y enemies once you get used to how all the paths work.

Damage per second is analagous to Effective HP from the previous section. The "Speed" stat is actually the number of seconds interval between attacks. Increasing "speed" by 10% increases Damage per second by 10%, just as increasing "Damage" does.

For maximizing a character's damage output, what counts then is looking at how Damage and Speed interact with other things.

First things first --- most character's active abilities scale with their Damage, not their Speed. Adding Speed only affects auto-attacks, not the MP charge rate and active ability rate. Also, putting Ability Orbs into a character usually increase the magnitude of the scaling.

Therefore placing damage up items on a character with a high-scaling active ability in which you've invested ability orbs is generally the optimal way to maximize both what you get out of the item and what you get out of the ability orb in terms of damage. Give +10 attack to a character with a 100% damage ability adds 10 damage to that ability, but the same item on a 450% damage ability adds 45 damage.

On the other hand, some items have a proc -- consider another item I'll take 100% of the time when I see it, Scourge of the Wastes. Its effect happens on every single attack, regardless of how much damage that attack does. So all you care about for such a thing is Speed. High speed attacks with effective procs (e.g. burns, poisons, etc.) have a lot of power.

When you look at building damage from an ability you also have to consider the ability's MP cost, which is the character's "MP" stat. Characters gain 10MP per second in general, so the MP cost divided by 10 equals the number of seconds interval between casts. Think of this similarly to Damage per second when deciding where to invest your stat ups and ability orbs to maximize what a character can do with their abilities.

A lot of Astronarch revolves around controlling the tempo. Many items and abilities get worse or better for you or for the enemy as time goes on.

Consider Barba the Exalted in Act 2. At the start of the fight the guy can't hurt you -- every couple of seconds he slashes your character with the most health. So he goes round-robin, tapping everybody on the shoulder once. But as the fight goes on his speed ramps up until he's slashing once every 0.6 seconds, and you slide exponentially from safe to doomed.

There are a lot of good strategies that revolve around using time to your advantage. Just for a taste, consider this 3-character team composition:

Ranger with high Defense
Illusionist with high Health and/or Cast Speed
Berserker with high Speed

At the start of the fight the Ranger summons his turtle. The turtle is only going to block a few hits -- if you're lucky he gets his Divine ability off and buys you 1.5 extra seconds. His only job is to buy enough time for the Illusionist to summon an Illusion. If he succeeds before the turtle dies, the enemy's next target becomes the illusion, whose health also has to be gone through before the enemy can make it to any of your actual characters. Now hopefully you're able to place your characters so that the Ranger himself becomes the next target. He goes down, but while he's going down the Illusionist gets ANOTHER illusion out. The illusion goes down; the illusionist goes down.

All this takes time, during which your Berserker has been getting stronger, and stronger, and stronger, slowly shifting the balance of power in your favor. You've bought him time to become unstoppable.

Consider giving the Berserker a Reverie Totem, the one that gradually slows EVERYBODY else down, for something wild. Just watch out for Disarm, Stun, and powerful Actives like on the end boss.

Or consider an inversion of that strategy:

Ranger with balanced stats
Assassin with high Speed and procs
Pyromancer with Royal Arbalest

Throw in Hag's hex bag, Yuki's hurricane, Fenrir's axe, and other things which jump out at the start of the fight.

All three of these characters can target a back-liner together, so they nuke an enemy healer or pain-in-the-butt target in the first few seconds of the fight, preventing the enemy's mechanisms of tilting the balance of power in THEIR favor.

Finally consider potions -- by definition these are an important tempo-shifter in your favor, and learning when you would need a potion to win and when you wouldn't win even with a potion is great experience and strategy.

I won't go into too much detail here, as it's a matter of experience. You get a feel and a preference for when you want a regular fight and when you want an Event, and which Events you're hoping for.

As a general rule, Events are more valuable when you already have a decent stock of gold and/or morale. At low gold and morale fights are usually preferable.

Finally this: Certain enemies have extremely potent abilities that have to be neutralized for you to have a chance. Again, this is a matter of experience, but at a certain point you simply can't make a team without planning at the beginning for how you're going to handle the end boss.

SPOILERS:

The guy gives all your characters 5 stacks of Revenge, which cause them to take 50% of the damage they deal. Meanwhile he has WAY more health than all your characters put together. So you need a potent way of shielding away or healing away the revenge damage, or removing the Revenge or Negating it or being immune to it on your key damage dealers, otherwise you're hosed before you begin, even if you go into the fight with what feels like a really strong team.

ALWAYS save a full belt of potions, either Cure Alls or Divines for the boss.

Corruption 20 is a whole world apart from levels 1-19. There are a few difficulty spikes along the way, but nothing like what happens at 20.

SPOILERS

Corruption 20 requires you to start with only 2 heroes, and finish with only 4. This dramatically changes the way strategies can work. Instead of being able to build around a tank / DPS / healer kind of trinity, you have to be blending roles right from the start.

It seems to me that there's no consistent way to win Corruption 20, although there are hundreds of consistent ways to lose. I think even perfect play requires a bit of luck to eke out a win. But the point at this level is that if you're not putting into practice all the principles that let you win often at the lower levels, you don't even have a chance.

I believe it's necessary to pass up some of the Elites on the first level. An early Elite may be flat out impossible to beat, but that doesn't mean your run is impossible to win. It may be important to get a feel for when you're strong enough to start tackling which fights. It may also be important to get a feel for when the game's power curve has left you too far in the dust and it's best to restart the run.

It will be absolutely necessary to check what boss you'll face at the beginning of the floor to make sure you have a plan.

I just scored my first win tonight on about my 6th attempt, after 1-trying or 2-trying most of the other Corruption levels below.

My team started with Druid and Ronin. I found the Druid could keep himself alive long enough for the Ronin to ramp up, and the Ronin's Disarm passive helped early on. I found that AoE DPS from the Ronin was absolutely critical to be able to win enough fights to generate items, gold, and morale to push through.

I then added Frostmancer, and finally Berserker. My end boss plan involved getting the Realm Tooth + Whirlwind Axes on the Berserker, and just for insurance I had a Symbiote and an Enchanter's Rod for Revenge immunity on the Ronin.

Good luck with this one, everyone, it's crazy!

This game is really a ton of fun. At first I was put off by the graphics but the game design depth in here is just lovely to behold once you start to wade into it.

Have fun everybody!

This section is just to write down some cool things I've discovered and/or brainstormed and/or heard other folks talking about (if so I'll credit if I can). Thoughts are unsorted for now, consider this a grab bag.

I think a lot of fun of the game is finding this stuff for yourself, so you might not want to read this section, I consider it kinda spoiler-y.

Join me in some brainstorming though if you like.

~~~~~

• Reverie totem can hose the final boss. His active ability first equalizes your party's HP, which means your lowest health folks get brought up, then it hits everybody. Reverie totem leaves the interval between his actual attacks to be gaping, so his only real damage comes from this, which is harmless if you have good heals running. Meanwhile by slowing them down you protect them from their own Revenge damage.
  
  
• Paladin plus Pyromancer is an obvious starter synergy.
  
  
• Druid plus Brawler is my favorite tank / healer combo; the Druid's attack boost on his heal synergizes with the brawler's Counter passive.
  
  
• Helm of the Mad King + Ascension Cloak lets you get a little boost off the Helm then safely pass the aggro on.
  
  
• Fiend + Reckless Dueling Blade is one of my favorites... The Fiend wakes up missing 70% of his health and the Dueling Blade becomes deadly.
  
  
• Making a 2-star item is usually better than having 2 1-star items because when you're working with synergies, value is multiplicative, not additive. You also have a chance to pick up 1-star items in rewards, and they'll compete for slots eventually with your 1-stars but not your 0-stars.
  
  
• If you haven't tried it yet, just for lulz try Pharoh's Mark with a lot of gold in the bank or Seeker of Virtue with a lot of morale. You deserve to see them in action before you decide if they're good/bad.
  
  
• The -15/-30/-45 defense on Impaler you can almost think of as a +15%/+30%/+45% damage boost on your active ability if you want.
  
  
• Save your potions as much as possible for elites and bosses, unless you have a morale crisis mid-floor. As for when in the fight to use them -- decide if you're in the most danger at the beginning or late phase of the fight. Are enemies ramping up? Or are you facing a ton of DPS at the beginning? Is the enemy hitting you with DoTs? Learn where the seconds count.
  
  
• On the same token -- You can literally count the number of seconds you can expect your tank to survive by comparing the incoming DPS to your effective HP to make strategic calls.
  
  
• Some items are more effective in regular encounters but become useless against bosses, and vice versa. So it's often great to keep a swap kit in reserve for your critical characters.
  
  
• The swap kit idea also applies to tempo -- in some fights, starting MP may be critical, in other fights you expect a long haul and ramp-up items will do better.
  
  
• By Act 3 Gladiator can achieve the highest effective HP of any tank. As a main tank in Act 1 he's OK -- a little tilted on the damage side.
  
  
• Swapping your roles around mid-run is usually a good strategy. E.g. you might have a Druid who starts as your tank, but you transition him to your healer. Often this pulls against the Passive / Active orbs -- e.g. the passive and active lend themselves to opposite roles -- so you always look for a blend of flexibility and lean-in.
  
  
• Formations deserve their own section, but in a nutshell, I think going 2/1, 3/1, and then 3/2 is often more flexible than 3/0, 4/0, 4/1, but 3/0, 4/0, 4/1 with an Assassin is easiest to get started with.