Bad mutations

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Version 0.30: This article may not be up to date for the latest stable release of Crawl.

Here is a list of all the bad mutations you can acquire. Although some may have situational uses, they are at best mixed blessings. Regardless, "bad mutation" is a technical term used by the game, not a qualitative judgement. Any of these can be acquired through any source of bad mutations.



Rank Effect Flavor
1 3% chance of berserking each time you attack in melee. You tend to lose your temper in combat.
3 Chance increased to 9%. You have an uncontrollable temper.

Often referred to as "berserkitis". Stacks additively with items of *Rage or wrath.

Species Notes: Formicids are exempt, because their stasis prevents berserk.

Bad mutation


Deformed Body

Rank Effect Flavor
1 Reduces body armour base AC by half. Armour fits poorly on your strangely shaped body.

Does not stack with Jiyva's Pseudopods mutation.
Does not affect AC from any other source (i.e. other equipment, armour enchantment, the protection ego, etc.).
Bonus AC from your Armour skill is still calculated based on the armour's full base AC.

Species notes: Nagas and Armataurs start with this mutation.
Draconians, octopodes and felids cannot gain this mutation as they cannot wear body armour.

Bad mutation


Rank Effect Flavor
1 Chance to shout when enemies enter line of sight (same noise as tt). You occasionally shout uncontrollably at your foes.
2 Greater chance for louder shouts. You sometimes yell uncontrollably at your foes.
3 Greatest chance for loudest shouts. You frequently scream uncontrollably at your foes.

Bad mutation


Rank Effect Flavor
1 You are sometimes teleported next to a monster. You are occasionally teleported next to monsters.
2 More frequent teleportation. You are often teleported next to monsters.

Species Notes: Formicids can not teleport and thus can not get this mutation.

Bad mutation

Heat Vulnerability

Rank Effect Flavor
1 rF- You are vulnerable to heat.
2 rF-- You are very vulnerable to heat.
3 rF--- You are extremely vulnerable to heat.

Qazlal may give you this mutation as a punishment.

Bad mutation

Cold Vulnerability

Rank Effect Flavor
1 rC- You are vulnerable to cold.
2 rC-- You are very vulnerable to cold.
3 rC--- You are extremely vulnerable to cold.
Qazlal may give you this mutation as a punishment.

Bad mutation

Consumable usage

No Unsafe Scrolls

Rank Effect Flavor
1 Taking damage has 1% chance to give -Scroll (which prevents reading scrolls). You occasionally lose the ability to read scrolls when taking damage.
2 Chance increased to 3%. You sometimes lose the ability to read scrolls when taking damage.

Note that -Scroll cannot be cancelled.

Bad mutation

No Unsafe Potions

Rank Effect Flavor
1 Taking damage has a 1% chance to give -Potion (which prevents drinking potions). You occasionally lose the ability to drink potions when taking damage.
2 Chance increased to 3%. You sometimes lose the ability to drink potions when taking damage.

Bad mutation

No Potion Heal

Rank Effect Flavor
1 Potions heal 50% of what they would normally. Potions are less effective at restoring your health.
2 Potions do not restore any HP. Potions cannot restore your health.

Includes potion of curing, potion of heal wounds, and potion of ambrosia.
Note that other effects (curing status, ambrosia MP regen) are unaffected. Also, Gozag's effects are unaffected.

Species information: Vine Stalkers start at rank 2.

Bad mutation



Rank Effect Flavor
1 A small chance for stat loss whenever you take damage. Your body sometimes deteriorates on taking damage.
2 Increased chance for stat loss. Your body often deteriorates on taking damage.

Bad mutation


Rank Effect Flavor
1 Gain further malmutations until trait expires. You have hidden genetic defects.
2 Same as previous level, though lasts longer. You have terrible hidden genetic defects.

Triggers about every 1/4 XL's worth of XP, providing another bad mutation. Every two activations it reduces its level by one.

Bad mutation


Rank Effect Flavor
1 Max HP -10% You are frail.
2 Max HP -20% You are very frail.
3 Max HP -30% You are extremely frail.

Bad mutation

Low MP

Rank Effect Flavor
1 Max MP -10% Your magical capacity is low.
2 Max MP -20% Your magical capacity is very low.
3 Max MP -30% Your magical capacity is extremely low.

Bad mutation

Reduced Attributes

Rank Effect Flavor
1 -2 to STR, INT or DEX You are weak
You are dopey.
You are clumsy.
2 -4 to STR, INT or DEX You are very weak
You are very dopey.
You are very clumsy.

While it's possible to gain this mutation multiple times, each attribute is limited to 2 ranks.

Bad mutation

Inhibited Regeneration

Rank Effect Flavor
1 No regular HP regeneration when monsters are in line of sight. You do not regenerate when monsters are visible.

Jiyva's regen and Trog's Hand function normally, though all other external regeneration sources fail.
For this mutation's history, see Inhibited Regeneration#History.

Species Notes: Ghouls start at rank 1.
Vampires have this mutation when Bloodless, and thus unable to get it randomly.

Bad mutation

Subdued Magic

Rank Effect Flavor
1 Spell Power-, Spell Success+ Your spells are a little easier to cast, but a little less powerful.
2 Spell Power--, Spell Success++ Your spells are easier to cast, but less powerful.
3 Spell Power---, Spell Success+++ Your spells are much easier to cast, but much less powerful.
Each level gives -20% (additively stacked, then multiplied) to raw spellpower and -2% (additive) to raw spell failure rate.

Generally, the impact will be less than -20% power and -2% failure, respectively.

Bad mutation

See Also


  • In 0.30, Heat and Cold Vulnerability became regular mutations.
  • In 0.29, No Unsafe Potions became a regular mutation. Many mutations were increased/reduced to 2 levels.
  • In 0.28, Devolution was introduced.
  • In 0.27, Blurry Vision was replaced with No Unsafe Scrolls.
  • Prior to 0.22, MP-Powered Wands was different and considered a bad mutation.
  • Prior to 0.20, the Inhibited Regeneration mutation had 3 ranks.
  • Prior to 0.17, the Forlorn mutation was available.
  • Prior to 0.15, the Slow/Fast metabolism mutations were available as random mutations.
  • Prior to 0.14 the Slow Movement mutation occurred randomly and levels 1 and 2 of the Slow Healing mutation cut natural regeneration by 33% and 66% respectively, regardless of enemy presence.
  • Prior to 0.13, Reduced Attributes could be acquired up to 14 times, giving you -1 per rank.