Bad mutations

Version 0.21: 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. Any of these can be acquired through any source of bad mutations.

Offensive

Berserk

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

MP-Powered Wands

Rank	Effect	Flavor
1	Automatically boosts wands, using 3 MP per zap.	You expend magic power (3 MP) to strengthen your wands.
Boosts the power of your wands by 33%. If you don't have enough MP, you'll use the wand unboosted.
Good mutation

Defensive

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

Screaming

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

Teleportitis

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

Consumable usage

Blurry Vision

Rank	Effect	Flavor
1	+5 auts to read scrolls.	Scrolls take you a little longer to read.
2	+10 auts to read scrolls.	Scrolls take you longer to read.
3	+20 auts to read scrolls.	Scrolls take you much longer to read.
Reading a scroll involves first the penalty from blurry vision, then the scroll takes effect, then the normal 10 aut delay for reading the scroll occurs. Replaced by No Unsafe Scrolls in 0.27.
Prior to 0.16, this mutation gave a 20%/40%/60% chance to fail all attempts to read books or scrolls.
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

General

Deterioration

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

Frail

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

• Good mutations
• Demonspawn mutations
• Jiyva mutations

History

Prior to 0.20, the inhibited regeneration mutation had 3 ranks.

Prior to ???, the slow metabolism mutation could be acquired, and the degeneration mutation had 3 ranks.

Prior to 0.17, the Forlorn mutation was available.

Prior to 0.14 the Slow 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.