Cosmic Star Heroine: Game Mechanics & Formulas Guide

How long do buffs last? Which buffs stack? How do weapons contribute to damage — compared to stats — compared to ability power?

Find these and other useful answers here.


Damage Formulas

The basic damage formulas for this game are pretty straightforward.

Simplified Model:

BASE DAMAGE = Ability Power * Key Stat * Weapon Power * Multipliers

There are many multipliers, from buffs, debuffs, weaknesses, hyper, equipment passives, etc. The vast majority of these are also multiplied together. (In a few cases, multipliers are added together instead. There are also a few that do not stack at all.)

Base damage is then reduced by defense. Defense provides a % reduction, and then a flat subtractive reduction, both based on the same defense stat.

Detailed Model:

ABILITY OUTPUT = (Ability Power * Key Stat) + 15
WEAPON OUTPUT = Weapon Power + (Level * 2)

BASE DAMAGE = Ability Output * Weapon Output * Multipliers

Unless the attack is Piercing, Base Damage is subjected to ARMOR REDUCTIONS in this sequence:
1) % based on armor
2) Flat subtraction based on armor
3) Multipliers from defend and wall effects

Ability Power just depends on the ability (or shield program) you use.

Key Stat also depends on the ability used. It is almost always a single stat, but there are a few abilities that effectively use the average of two or more stats. (This is most prominent in Chahn’s Gunmancy skills.)


The in-game descriptions are accurate! This is so rare in RPGs. A little more detail on what they do:

  • All stats increase damage for abilities that rely on them. (For Cunning, this is just the two damage-dealing items.) Mostly proportionate to stat level (see above).
  • Physique and Sparke reduce damage taken by physical and magical attacks. (Some attacks, mostly “tech” style, use half reduction from both stats.) Semi-proportionate to stat level (see defense section).
  • Base Physique increases Max HP. Passive/buff bonuses to physique do not affect this.
  • Every 10 points of Sparke grants 5% Style at the start of combat.
  • Hacktitude unlocks shield programs.
  • Cunning increases the success power of almost all ailments, proportionate to stat level. For poison, it instead determines the damage dealt.
  • Cunning increases resistance to stun, charm, disarm, vulnerable, and enrage, semi-proportionate to stat level.
  • Cunning has an extremely tiny effect on Speed, which is effectively limited to determining the order the PC’s (and normal-speed enemies) act in.

Defense Power

Regular defense power, both physical and magical flavors, is calculated as follows:

DEFENSE VALUE = (Stat + Level) * (Shield + Level) * Penalties * Buffs

Stat is Physique or Sparke for physical or magical defense, respectively.
Shield is the physical or magical defense stat of your equipped shield.

This formula is why you usually don’t see a ton of variance in damage taken, but if you have Dave with the Dark Shield next to Z’xorv with an endgame shield, it’s a world of diference.

There are only 2 possible penalties, Rust and Bum Rush. Both cut the defense value in half.

Defense buffs, unlike most buffs, are all added together before being applied:

+25% Fortify (Chahn, party-wide)
+25% Unified Defense (Psybe, party-wide)
+25% Martyr (Finn, party-wide — this appears to be a bug, as the ability says +50%)

+40% Solid Stance (Protector shield)
+50% Heroine Aura (Alyssa)
+75% Exoskeleton (Psybe)
+75% Defense Stance (Finn)

The defense value calculated above determines two different reductions: first a percentile reduction, then a flat subtractive reduction. The percentile reduction increases at certain milestones, while the subtractive reduction increases smoothly between those milestones:

Value % Subtract —– — ——– 1000 5% -10 2500 10% -21 4500 15% -25 7000 20% -30 10000 25% -36 13500 30% -43 17500 35% -51 22000 40% -60 27000 45% -70 32500 50% -81 38500 55% -93 45000 60% -105 52000 65% -119 59500 70% -137 67500 75% -149

Enemies also have defense values, which vary with difficulty. Late-game on Super-Spy, 13500 is very common, and 22000 is the highest that you’ll have to meaningfully deal with.

By the mid to late game, you can safely estimate Piercing attacks will deal 140-160% the damage of identical non-piercing attacks.

What’s the impact of player defense values in practice? Late-game, Dark Shield Dave might reach 5400, for 15% and -27. Z’xorv with a good shield can easily approach 40,000, for 55% and -93.

Applying Fortify or Unified Defense with boost Dave to 6700 — in this unfortunate example, giving him just a flat 3 points of damage reduction! It will boost Z’xorv to 50,000, reducing his damage taken by a relative 11% before subtraction and an extra 20 points blocked after that.

Ultimately, these effects will reduce damage the most noticeably when you have high defensive stats and are taking low to moderate damage to begin with.

Elemental Defense and Vulnerability

If the target resists an element, damage is reduced or increased here, in most cases by -50%.

Orson’s Decimator (which covers 3 elements) provides -33% instead of -50%.

The Anti-Elem passive on Finn’s Flamethrower causes Finn’s elemental resists to provide an additional 50% reduction (multiplicative).

(All PC equipment passives that grant increased elemental damage also provide resistance. Note that the “increased elemental damage” aspect is applied earlier, before defense power.)

If an attack consists of multiple elements, the modifiers for each element are added together, then applied to the entire attack.

For example, if Orson hits two weaknesses with Meteor, he will deal double damage. If he hits one weakness and one resistance, he will deal normal damage.

Defend Commands

Finally, damage is reduced if you are defending. Defend commands reduce your damage by the percentage listed on the command.

Chahn’s Protective Barrier works for the whole party, but does not stack with any individual Defend command.

Alyssa and Chahn have equipment that increase the percentage by +20 and +15, respectively. (Chahn’s applies only to her, not to other party members, when she uses Protective Barrier.)

Notably, Alyssa has a base 50% Defend command, which can therefore provide an extra 70% damage blocking. In combination with Regeneration and Poison, this can sometimes make it a viable strategy to let poison kill the enemy, while Alyssa survives (alone) by defending every turn.

Wall Effects

After defend is applied, damage is dealt first to any existing wall effects. If it doesn’t use up the wall effect’s HP, that effect remains, and the PC takes only 1 damage. If it does use it up, the PC takes the unabsorbed damage.



Poison, Rust, Curse, and Enrage are permanent (unless cured).
Stun, Charm, Vulnerable, and Disarm last for one trigger.

Effectiveness (Most Ailments)

As the game describes, every character has “Ailment HP” for each ailment. When these are depleted, the ailment is inflicted. Ailment HP are reset to a higher point, so it takes more effort to inflict the same ailment repeatedly.

Enemy Ailment HP is reduced by 50% on Tourist, and by 25% on Normal.

AILMENT EFFECTIVENESS = Ability Power * (Cunning + 15) * Multipliers

The list of multipliers is much shorter. Half the ailments only need to be applied once, and the one-turn ailments stop being worth the effort as their ailment HP rises, so boosting this number is really only interesting for Poison.


Poison is always successfully applied, unless the target is immune. Instead, Poison’s effectiveness determines its damage dealt per turn. This effectiveness is reduced, proportionately, by the target’s Ailment HP for Poison. The Ailment HP does not have to be “overcome” and it is not reset after successful application.

Compared to the damage formula, the ailment formula has fewer multipliers that rise over the course of the game. This means that Poison is very powerful in the early game, but becomes less useful by the end.

Poison Ability Powers
60% Poison Mist (Item)
90% Snake Strike (Lauren, Shield)
110% Infect (Z’xorv)
130% Plague (Lauren, Shield)
150% Sludge (Dave Enviro-Hack)

Cunning Multipliers (Additive)
+35% Spy Sense / +75% specific Enviro-Hack (don’t stack with each other)
+60% FAQ
+35% Buffz / +25% Balance (don’t stack with each other)

Poison Ailment HP Modifier
Lauren’s Siren passive reduces poison resistance by -20. 50% resistance becomes 30% resistance; 0% resistance becomes 20% extra damage taken. This effect applies regardless of which PC is attacking.

Poison Multipliers
x2.0 Hyper (no other hyper multipliers)
x2.0 Style (at 100%+; burst is never checked)
x2.5 Dark Mist (from shield, may be applied by another ally)
x2.0 Accuse (applied by Orson)

x1.5 Enviro (Dave Enviro-Hack only)
x2.5 Pwn (Dave only)
x1.5 Poison Up (Lauren only)
x1.25 Ailment Up (Arete only)
x1.5 Item Up (Arete only), or x1.25 from shield
x2.0 Chemist (Item only)
x1.25 Donata Sparks (Item only)

Looking at max Poison output, for user-specific options, we get:
Lauren Ability 130% x1.5 = 195%
Arete Item 60% x4.69 = 281.4%
Lauren Item 60% x4.69 = 281.4%
Dave Shield 130% x2.5 = 325%
Dave Item 60% x7.81 = 468.6%
Dave Sludge 150% x3.75 = 562.5%

Additionally: as Orson, Lauren, Dave, and Alyssa all have ways to add to the user’s poison power, having Arete in the party means you miss out on one of those — Lauren’s is the least impactful. (Additionally, using Donata Sparks means you miss out on a tiny increase from having your Support boost Cunning.) Lauren’s Cunning is higher than Dave’s, but this isn’t nearly enough to overcome the advantage he gets from Pwn.

Sludge, unfortunately, isn’t available in the places where it would be truly useful.

At level 50, Dave will have around 70 base Cunning. If we do some math with the other modifiers, we can get his Cunning up to 161, with multipliers of 150% x75 for Sludge, or 60% x156.25 for the item. This gives us a base effectiveness of:

Sludge: 166 x75 at 150% = 18,675 damage
Item: 161 x156.25 at 60% = 15,093 damage

Against enemies with base 0% or 50% resistance to poison, we get:

Sludge = 22410 or 13072 damage per round
Item = 18111 or 10565 damage per round

This is pretty amazing. It may still be less effective than stacking damage multipliers on someone like Dave or Z’xorv, and it might be worth sacrificing the extra 20% damage from Lauren in exchange for a healer like Psybe or Chahn, particularly since you need to survive to benefit from all those rounds of poison. Of note, when Sludge isn’t available, this also requires giving Dave the Chemist shield, which provides terrible defense at that point, and using your support slot on Donata Sparks.

Stat Buff Stacking

Key stats are multiplied into the damage formula with only a small buffer, so increasing stats will have a nearly proportional effect on damage output, especially at higher levels.

Additive buffs, from equipment and support, apply first. Multiplicative buffs are summed together before being applied, and then apply to everything.

+35% Buffz or +25% Balance (do not stack)

+35% Buffz or +25% Balance (do not stack)

+35% Buffz or +25% Balance (do not stack)
+50% Brains (rarely practical)

+35% Buffz or +25% Balance (do not stack)
+35% Spy Sense or +75% Enviro-Hack Cunning buff (do not stack)
+60% FAQ

Damage Multiplier Stacking

Here’s the fun part 🙂

There are tons of passives and buffs that can multiply your damage.

All multipliers in different categories (below) stack by multiplication. i.e., Two x3 multipliers would increase damage by a total of x9. Multipliers within a given category sometimes stack by addition instead — this is noted here where it applies.

Most multipliers can only be applied once. Two copies of the identical buff, or the identical equipment passive, will not stack. This is true even if they are at different strengths.

The primary exception to this is that buffs, equipment passives, and support character effects always stack across these 3 categories. For example, +5 Cunning from equipment and a support will stack, and if you then apply FAQ for +60% Cunning, both +5 bonuses will be included in calculating +60%.

Style Multipliers

x1.00 +.01 for every 1 point of Style, up to 100 for x2.00 (up to 120 for x2.20 with Sue weapon)

Single PC Burst (multiplied with “Always” multiplier):
x1.00 +.01 for every 1 point of Style, up to 300 for x4.00

Heroine Shield Burst (multiplied with “Always” multiplier):
x2.00 +.01 for every 2 points of Style either PC has, up to 300 for x5.00

(This is the only impact the second PC ever has on unite ability damage.)

Hive Mind always applies to the “Always” multiplier, but will never apply to the burst multipliers.

Hyper and Desperation Multipliers

x2.00 Hyper
x1.50 Hyper Program (Dave weapon)
x1.40 Hyper Awareness (Psybe)
x1.25 Hyper Up (Alyssa weapon or Sue Showboat)

x1.50 Desperation Mode
x1.50 Marco Xol
x1.33 Desperate (Lauren weapon)
x2.00 Desperate (Finn weapon)

All stack by multiplication.

Program Up

x1.35 Program Up (shield)
x1.50 Bandwidth (Dave)
x2.00 Debug (Arete)
x1.50 LAN Party (+.01 for every 4 points of Style either PC has on cast, up to 150 for x3.00)
x1.50 Teamwork (Alyssa accessory, Unites only)

Program Up and Bandwidth stack additively.
Debug and LAN Party do not stack with each other.
Outside of those two cases, these stack by multiplication.

Additive Damage Multiplier

The following buffs and bonuses are added together to form a single damage multiplier.

+0.15 Solidarity (Alyssa weapon, affects any party member at 300% Style)
+0.25 Mortify (Clarke party buff, when he is dead)
+0.25 Deadly (Clarke accessory, when Mortify is active)
+0.50 Poised (shield, first turn)

+0.10 Unified Offense (Psybe party buff)
+0.15 Silver Bullet (Chahn party buff)
+0.25 Alliance (shield)
+0.33 Inspire (Alyssa or shield, effect halved if cast on Alyssa)
+0.50 Self-Motivate (shield) – note the penalty is a flat 100 CR!
+0.70 Cheat Code (Dave)

+0.35 Feint (Sue only)
+0.40 Hot Blooded (Z’xorv only)
+0.40 Stinging Fly (Finn only, unclear if buff is intentional)
+0.50 Heroine Aura (Alyssa only)
+0.75 Chant (Orson only)
+1.00 Prepare (shield, user only)
+1.00 Limiter Release (Clarke only)
+1.50 Avatar (Psybe only)

+0.20 Powers Combine (Alyssa accessory)
+0.30 Damage Up (Z’xorv weapon)
+0.33 Revenge (Sue weapon, per dead party member, up to +0.99)
+0.50 Charge Up (Sue weapon, after defending)

Other Universal Multipliers

These stack with everything by multiplication.

x2.00 Chemist (Arete or shield)
x1.50 Item Up (Arete weapon or accessory) or x1.25 (shield)
x1.25 Donata Sparks

x1.25 Ron Cynbel (not +20% as displayed, Robot Bane)
x1.25 Noct Egret (not +20% as displayed, Organ Bane)
x1.25 Ailment Bane (shield)
x1.25 Ailment Up (Arete weapon)
x1.25 Enrage Bane (Z’xorv weapon)
x1.30 Silver Bullets (Chahn party buff, vs Astral)
x1.50 Disarming (Finn weapon, Disarm Bane)
x1.50 Organ Bane (Z’xorv accessory)
x1.50 Astral Bane (Chahn accessory) or x1.40 (Orson weapon) or x1.25 (shield)
x1.50 Poison Bane (Chahn weapon)
x1.50 Robot Bane (Chahn, Dave, and Arete weapons or Arete accessory) or x1.25 (shield)

x1.33 Fire/Wind/Ice Up (Orson weapon)
x1.50 Water Up (Alyssa weapon or accessory, or shield)
x1.50 Fire Up (Chahn and Finn weapons)
x1.50 Ice Up (Arete weapon)
x1.50 Electric Up (Clarke weapon or shield)
x1.50 Wind Up (Lauren weapon)
x1.50 Earth Up (Sue accessory)
x1.60 Ice Up (Z’xorv accessory)

x2.00 Oil Spill (Clarke)
x1.50 Gumshoe Shift (Orson only) — note, cannot coexist with Shadow Shift
x1.50 Bully (Z’xorv accessory)

x2.00 Vulnerable ailment on target

Elemental Weakness

Elemental weakness (and resistance) are applied after armor. Other than that, they basically act as universal multipliers. If you hit multiple weaknesses at once, the +50% effects stack additively. (Element Up is an unrelated effect, covered above.)

Arete’s Mutate ability can create elemental weaknesses. It will create one new weakness on each use. It always attempts to create them in the same order: Water, Fire, Ice, Lightning, Wind, Earth.

Stat Buffs

These have a similar impact as multipliers, but the exact math is slightly different since they apply to the Key Stat portion of the damage formula.

Multiple buffs that affect the same stat — for example, Spy Sense, FAQ, and Buffz — normally have an additive effect (in this case, 0.35 + 0.60 + 0.35 = x2.3 multiplier to Cunning).

Buff Duration

Some of these are listed in the ability description, but many are not, and there are a few inaccuracies.

Effectively permanent
Buffer Zone, Injection
Showboat (!)
Mic Drop
Mutate, Astralize
Debug, LAN Party
Hive Mind
Gumshoe Shift, Shadow Shift (mutually exclusive)
Smelly Cheese

Effectively permanent until used
Surprise Stash, Wireless
Save and Quit
Pwn, Accuse, Dark Mist
Oil Spill
Force Field, Absorb Shield, Wall, Aegis
Pain Pill

8 turns
Stinging Fly

6 turns
Inspire, when caster is Hyper — AFAIK this is the only buff that benefits from a Hyper caster
Hyper Awareness
Add Element (abilities)
Sea Wall

5 turns

4 turns
Rock Solid, Defense Stance
Swift Breeze

3 turns
Inspire, Heroine Aura, Limiter Release, Hot Blooded, Alliance
Spy Sense
Silver Bullet
Bum Rush
Balance, Buffz
Duet (regeneration)
Solid Stance

2 turns
Counter (Sue) — the description lies, it does not last 9 turns 🙁

1 turn
All-Out, Adjust Tie
Feint, Cheat Code, Chant, Prepare
Sudden Stab


Speed affects how long you have to wait between turns, and therefore how many turns you get.

Cunning technically increases Speed, which is why it determines normal turn order within the party. However, the increase is so tiny that it will basically never lead to any extra turns.

Some bosses have a higher than normal Speed by default, especially late-game and especially on higher difficulties.

The following effects can modify a PC’s delay between turns. (The turn itself is always instantaneous.) All of these modifiers are multiplicative. Lower delay = more turns.

135% Rust

95% Paws
90% Speed Up (Trickster shield)
80% Brisk Song
66% Swift Breeze (does not apply if Sudden Stab is active on a turn, but is not removed by it)
50% Sudden Stab
50% Jitterbug

Paws, Speed Up, and Brisk Song are significant effects as they can last the entire battle.

Jitterbug will basically earn Clarke back the turn he used to cast it, which means he gets a free hyper bar out of it.

Swift Breeze will basically earn Lauren back that 1 turn plus 1/3 of a turn, so she gets 1 1/3 free hyper bars out of it.

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