Skip to main content

​
Perk Interactions

Perks interact in complex ways - some synergize multiplicatively, others conflict or override each other. Understanding these interactions is critical for optimal builds.

​
Multiplicative Damage Stacking

​
Bullet Damage Perks

From src/crimson/creatures/damage.py:131-136, bullet damage perks stack multiplicatively: 
# Applied in sequence:
1. Uranium Filled Bullets: damage *= 2.0
2. Living Fortress: damage *= (fortress_timer * 0.05 + 1.0)  # 1.0x to 2.5x
3. Barrel Greaser: damage *= 1.4  
4. Doctor: damage *= 1.2
Maximum Stack: 2.0 × 2.5 × 1.4 × 1.2 = 8.4x bullet damage Example - Plasma Rifle (5.0x weapon): 
Base damage: ~332 (point-blank)
With all perks: 332 * 8.4 = 2,788 damage per shot
Applies To: All bullet-type weapons (damage type 1) Does NOT Apply To: Fire weapons (Flamethrower), Ion weapons, special weapons

​
Fire Damage

Pyromaniac: 1.5x multiplier to fire weapons Applies To: Flamethrower, Blow Torch, HR Flamer (ammo_class=1) Does NOT Stack: Fire weapons can’t use Uranium/Barrel Greaser/Doctor/Living Fortress (bullet type only)

​
Ion Damage

Ion Gun Master: 1.2x damage + 1.2x blast radius Global Effect: Any player’s ion damage scaled (not just perk owner in co-op) Applies To: Ion Rifle, Ion Minigun, Ion Cannon, Ion Shotgun (ammo_class=4)

​
Reload Speed Stacking

​
Reload Perks

Fastloader: reload_time × 0.7 (30% faster) Stationary Reloader: reload_time × 0.33 (3x faster when not moving) Anxious Loader: -0.05s per fire button press Weapon Power Up Bonus: reload_time × 0.5 (2x faster)

​
Stacking Examples

Fastloader + Stationary Reloader: 
Base reload: 2.0s
Fastloader: 2.0 * 0.7 = 1.4s
Stationary: 1.4 * 0.33 = 0.462s (77% faster than base!)
Fastloader + Weapon Power Up: 
Base reload: 2.0s
Fastloader: 2.0 * 0.7 = 1.4s
Weapon Power Up: 1.4 * 0.5 = 0.7s
All Reload Bonuses: 
Base reload: 2.0s
Fastloader: 2.0 * 0.7 = 1.4s
Stationary: 1.4 * 0.33 = 0.462s  
Weapon Power Up: 0.462 * 0.5 = 0.231s
Anxious Loader: 0.231 - (N * 0.05) where N = button presses
Can achieve sub-0.1s reloads with full stack!

​
Fire Rate Stacking

​
Fire Rate Modifiers

Fastshot: shot_cooldown × 0.88 (12% faster) Sharpshooter: shot_cooldown × 1.05 (5% SLOWER - trade-off) Weapon Power Up Bonus: shot_cooldown × 0.5 (2x faster)

​
Stacking

Fastshot + Weapon Power Up: 
Base cooldown: 0.2s (5 shots/sec)
Fastshot: 0.2 * 0.88 = 0.176s (5.68 shots/sec)
Weapon Power Up: 0.176 * 0.5 = 0.088s (11.36 shots/sec)
Fastshot + Sharpshooter (anti-synergy): 
Base cooldown: 0.2s
Fastshot: 0.2 * 0.88 = 0.176s
Sharpshooter: 0.176 * 1.05 = 0.185s
Net result: Still faster than base, but less than Fastshot alone
Sharpshooter’s accuracy benefit may outweigh the fire rate penalty.

​
Dodge Perks - Override Behavior

​
Dodger vs. Ninja

Dodger: 20% dodge chance (1-in-5) Ninja: 33% dodge chance (1-in-3), requires Dodger Interaction: Ninja overrides Dodger completely From perk 40 description: “Overrides Dodger when both are owned” You Get:
  • Pick Dodger: 20% dodge
  • Pick Dodger then Ninja: 33% dodge (NOT 53% or 48%)
Why Pick Dodger? It’s a prerequisite for Ninja. You must have Dodger to get Ninja offered.

​
Regeneration Perks

​
Regeneration + Greater Regeneration

Regeneration: 0.5 HP/sec average (50% chance per frame to heal +dt) Greater Regeneration: 2x heal amount when tick triggers (~1 HP/sec average) Requires: Regeneration (prerequisite) Stacking: Greater Regeneration modifies Regeneration’s heal amount, doesn’t add separate healing

​
Death Clock Clears Regeneration

From perk 47:
“On pick, health is set to 100 and Regeneration / Greater Regeneration are cleared.”
Effect: Picking Death Clock removes both regen perks permanently Blocked: Death Clock active prevents Regeneration/Greater Regeneration from being offered

​
Poison Perks

​
Veins of Poison → Toxic Avenger

Veins of Poison: Creatures that melee you get poisoned (60 damage/sec) Toxic Avenger: Upgrades poison to 180 damage/sec, requires Veins of Poison Stacking: Toxic Avenger replaces Veins of Poison’s 60/sec with 180/sec (3x stronger) Combined with Poison Bullets:
  • Poison Bullets: 12.5% chance to poison on projectile hit (60/sec or 180/sec)
  • Veins of Poison/Toxic Avenger: Guaranteed poison on melee contact
Both Active: Enemies can be poisoned from bullets OR melee, both use same damage rate

​
Movement Speed Interactions

​
Speed Modifiers

Long Distance Runner: Extends cap from 2.0 to 2.8 while running Alternate Weapon: -20% speed when perk active Speed Bonus: Temporary speed multiplier Reflex Boosted: Game time scale × 0.9 (affects effective speed)

​
Stacking

Long Distance Runner + Speed Bonus: 
Normal cap: 2.0
Long Distance Runner cap: 2.8
With Speed Bonus: Can exceed 2.8 temporarily
Alternate Weapon Penalty: 
Base speed: 180 units/sec
Alternate Weapon: 180 * 0.8 = 144 units/sec
Long Distance Runner: Can still ramp to 2.8x cap (but of 144 base)
Alternate Weapon’s penalty applies to base speed, then Long Distance Runner multiplies from that reduced base.

​
XP Gain Stacking

​
XP Multipliers

Bloody Mess / Quick Learner: +30% XP from kills (1.3x) Lean Mean Exp Machine: +10 XP per 0.25s (passive generation) Double Experience Bonus: 2x XP multiplier (timed) Instant Winner: Immediate +2500 XP (stackable perk) Grim Deal: +18% of current XP total, then death

​
Stacking

Bloody Mess + Double Experience: 
Creature XP: 100
Bloody Mess: 100 * 1.3 = 130
Double Experience: 130 * 2 = 260 XP total
Lean Mean Exp Machine Stacking: 
1 copy: 10 XP per 0.25s = 40 XP/sec
2 copies: 20 XP per 0.25s = 80 XP/sec
3 copies: 30 XP per 0.25s = 120 XP/sec
Linear stacking - each pick adds another +10 XP/tick.

​
Perk Expert + Perk Master

Perk Expert: Selection pool 5 → 7 choices Perk Master: Requires Perk Expert, claims to “double” but also shows 7 choices Actual Behavior (from source analysis): Both add +2 to selection pool You Get:
  • Base: 5 choices
  • Perk Expert: 7 choices
  • Perk Master: 7 choices (NOT 14)
Bug or Intended? Description says “doubling” but implementation is +2. Likely description is wrong.

​
Ammunition Perks Conflict

​
Ammunition Within vs. Regression Bullets

Ammunition Within: Fire during reload, costs HP Regression Bullets: Fire during reload, costs XP Both Owned: Regression Bullets takes priority (from perk 35 description) Reload Restart: Both perks prevent reloading mid-reload (must finish or deplete completely)

​
Trade-Off Perks

​
Instant HP Reduction

Thick Skinned: HP → HP × 2/3, future damage × 2/3 Breathing Room: HP → HP × 1/3, kills all on-screen enemies (no XP) Infernal Contract: HP → 0.1, grants +3 levels Interaction: These stack (can pick multiple) Example - Thick Skinned then Breathing Room: 
Start: 100 HP
Thick Skinned: 100 * 2/3 = 66 HP
Breathing Room: 66 * 1/3 = 22 HP
Dangerous combo!

​
Death Clock Conflicts

Death Clock Active: Blocks offering of:
  • Regeneration
  • Greater Regeneration
  • Thick Skinned
  • Highlander
  • Jinxed
  • Infernal Contract
  • MediKit spawns disabled
Reason: These perks would interfere with the 30-second death timer mechanic

​
Co-op Perk Sharing

In two-player mode: Shared: All perks apply to both players when either selects Living Fortress Stacking: Each player’s fortress timer contributes multiplier 
Player 1 timer: 20s → 2.0x multiplier
Player 2 timer: 10s → 1.5x multiplier
Combined bullet damage: base * 2.0 * 1.5 = 3.0x
Pyromaniac Bug: Original checks only player 1’s weapon for offering condition (use —preserve-bugs) Regeneration Bug: Original only heals player 1 and repeats by player count (use —preserve-bugs)

​
Perk Availability Conflicts

​
Quest Mode Exclusions

These perks never appear in quest mode:
  • Alternate Weapon (perk 9)
  • Grim Deal (perk 8)
  • Final Revenge (perk 19)
  • Highlander (perk 41)
  • Breathing Room (perk 46) - two-player only

​
Two-Player Exclusions

These perks never appear in two-player:
  • Grim Deal (perk 8)
  • Fatal Lottery (perk 15)
  • Random Weapon (perk 16)
  • Final Revenge (perk 19)
  • Highlander (perk 41)

​
Conditional Suppressions

Plaguebearer: Suppressed in hardcore quest 2.10 Poison Bullets: Suppressed in hardcore quest 2.10 Veins of Poison: Suppressed in hardcore quest 2.10 Pyromaniac: Only offered when player has Flamethrower equipped

​
Optimal Synergy Builds

​
”Glass Cannon” Build

Goal: Maximum damage output Perks:
  1. Uranium Filled Bullets (2x)
  2. Barrel Greaser (1.4x)
  3. Doctor (1.2x)
  4. Living Fortress (2.5x max)
  5. Fastshot (1.12x fire rate)
  6. Fastloader (0.7x reload)
  7. Ammo Maniac (+25% clip)
Result: 8.4x bullet damage, 12% faster fire, 30% faster reload, 25% more ammo Weapon: Plasma Cannon (28x) → ~15,640 damage per shot Weakness: No defense perks, standing still required for max damage

​
”Unkillable Tank” Build

Goal: Maximum survivability Perks:
  1. Dodger (20% dodge)
  2. Ninja (33% dodge, overrides Dodger)
  3. Regeneration (0.5 HP/sec)
  4. Greater Regeneration (1 HP/sec)
  5. Thick Skinned (damage × 2/3)
  6. Unstoppable (no knockback)
  7. Doctor (shows enemy HP)
Result: 33% dodge, 1 HP/sec regen, 33% damage reduction, no knockback Math: 
Effective HP: 100 / (0.67 * 0.67) = 223 HP (dodge + thick skinned)
Regen: 1 HP/sec = 60 HP/min sustain
Weakness: Lower damage output

​
”XP Farming” Build

Goal: Maximum level gain Perks:
  1. Bloody Mess (1.3x kill XP)
  2. Lean Mean Exp Machine (40 XP/sec passive, stack 3x = 120 XP/sec)
  3. Perk Expert (more choices)
  4. Perk Master (more choices)
  5. Instant Winner (2500 XP repeatable)
  6. Bonus Magnet (more bonuses)
Result: Fast leveling, many perk choices, frequent bonuses Strategy: Prioritize leveling over survival to snowball perk advantage

​
”Crowd Control” Build

Goal: Area damage and control Perks:
  1. Radioactive (passive 100-unit aura)
  2. Plaguebearer (infection spread)
  3. Hot Tempered (periodic plasma ring)
  4. Angry Reloader (plasma ring on reload)
  5. Man Bomb (stand still 4s explosion)
  6. Pyromaniac (1.5x fire damage)
Weapon: Flamethrower (synergy with Pyromaniac) Result: Constant passive damage from multiple sources Gameplay: Stand still to trigger Man Bomb, rotate slowly, enemies die from aura/plague/rings

​
Source Code References

  • src/crimson/perks/ids.py - Perk flags and availability
  • src/crimson/perks/impl/ - Perk implementation details
  • src/crimson/creatures/damage.py - Damage modifier stacking order

Build docs developers (and LLMs) love

Get started for freeTalk to us