| The Dungeon contains many sources of mutagenic radiation and magical contamination, which may cause your character to gain semi-permanent mutations if affected. You can use the 'A' command to view a list of any mutations that you have acquired. Individual mutations can be examined in further detail by pressing the letter they are labelled with.
Many mutations are actually beneficial to your character, but there are plenty of nasty ones as well. Some mutations have multiple levels, each of which counts as a single mutation.
It is more difficult to get rid of bad mutations than to get one. Using potions of mutation will remove a number of your current mutations, but will give you more mutations. These might be better to your taste. However, the only sure-fire ways is to join the gods Zin or Jiyva, each of whom provides some remedy against mutations.
Mutations are genetic oddities you may receive during your travels in the dungeon. Often acquired at random, they may be helpful or debilitating. To learn specifics about each mutation, see the full list of mutations or read:
Mutations induce various properties to your character, good or bad. Robust increases your max HP, Frail reduces it. Most species' gimmicks are defined by their starting mutations. Some mutations are transient (temporary), and are cured by gaining XP. Otherwise, mutations are permanent - they'll last until you have a way to remove mutations, usually potions of mutation.
Mutations from your species, whether on start or by level up, are considered "innate". These mutations can never be reduced or removed, though they may be improved (e.g. Minotaur's Horns 2 may lengthen into Horns 3). All other sorts of mutation you'll get can be removed freely.
Unless you are a Demonspawn, innate mutations do not contribute towards silver's damage bonus. For each "acquired" or demonspawn mutation you have, you take +5% damage from silver weapons (max. +75%).
Certain mutations conflict, so you can't have Fire Resistance and Fire Vulnerability at the same time. Also, mutations may conflict with species physiology: e.g. Octopodes can't get Claws or Horns, and Merfolk's tails don't support Talons or Hooves.
You can view all of your current mutations by pressing A. In the default settings for the A screen, mutations are displayed in different colors according to type:
- Innate mutations (from your species), good or bad, are blue. They can never be permanently removed.
- Mutations that are a combination of innate and acquired are displayed in cyan (good) or magenta (bad).
- Acquired good mutations are light grey.
- Acquired bad mutations are red.
- Transient mutations (temporary) are light magenta and between brackets.
- Mutations that are currently suppressed due to a transformation are dark grey.
There are many ways to gain external mutations - most are weighted towards the negative.
- Jiyva offers mutation gifts as you gain piety, including its own selection of mutations to followers.
- Xom can mutate you - depending on the action, it can be good, bad, or purely random.
- Potions of mutation removes 2-3 mutations, then gives 1-3. Each added mutation has a 60% chance to be good, and 40% chance to be random.
These sources ("malmutations") have an 80% chance to give you a bad mutation, and a 20% chance for a random one.
- The Malmutate spell is most common source of malmutation, cast by a small variety of monsters (neqoxec, shining eye, cacodemon, orb of fire).
- Mnoleg can malmutate you on melee attacks (25% chance).
- Any magic contamination over 5000 has a chance to mutate you. Contam-induced mutations will ignore mutation resistance 50% of the time (even bypassing Zin's protection).
- Jiyva's wrath can inflict bad mutations 100% of the time (no chance for random mutation).
These mutations are always bad, but are temporary, and will be cured by gaining XP.
- Hell's mystical force - Whenever you go downstairs in any of the 4 Hell branches, you have a 25% chance to get a transient mutation.
- Corrupting Pulse inflicts 1-2 transient mutations per use. Most often seen from wretched stars.
There are only a few ways to remove permanent mutations:
- A potion of mutation removes 2-3 mutations, then gives 1-3.
- Followers of Zin at 6* piety can drink potions to remove mutations. There's no chance to gain mutations, so there's no hit to piety.
- Jiyva has a 25% chance to remove a mutation level for each existing mutation, doubled if its a bad mutation, whenever it gifts new ones.
- One possible effect of Zin's wrath is to remove all of your good mutations.
If you get a conflicting mutation (e.g. getting Frail when you have non-innate Robust), they'll generally cancel each other out. Also, when you gain a random mutation, you may lose a mutation instead - see below for details.
Sources of mutation resistance stack multiplicatively:
- The rMut item property (found only on Hat of the Alchemist and lajatang of Order) gives a 66% chance to block mutations. The item property does not stack with itself.
- The Mutation Resistance mutation can block mutations based on its level. Level 1 gives a 66% chance to block incoming mutations. Level 2 also gives a 50% chance to block mutations from being removed. Level 3 gives a 100% chance to block incoming mutation and their removal (except from gods and contamination).
- Zin provides a
piety / 1.6% chance to block mutations. At 6* piety, this is 100% immunity (except for contamination).
- Ashenzari provides immunity to mutations that would shatter a cursed item, like Horns with a cursed helmet. This applies 100% of the time to non-innate mutations, even from contamination.
- Being undead (Ghoul, Mummy, Lich Form, but not Vampire) provides full, absolute immunity to mutation. Instead, you "rot" when mutating, causing stat drain.
When affected by "random" mutation (not "good" or "bad"), you have a
6.5% * non_innate_muts chance to prevent it. Each time you resist this way, you have 33% chance to lose a mutation. Xom ignores this 67% of the time.
The mutation system in Crawl can be quite punishing:
- Generally, the bad mutations are more bad than good mutations are good. Teleportitis randomly teleports you towards monsters, like you're hit by constant sourceless malevolence. No Unsafe Scrolls/Potions prevents using life-saving consumables. Meanwhile, the best good mutations are the likes of resistances & extra HP.
- Unless you worship Jiyva, the only reliable way to remove mutations are potions of mutation, which are finite and random. If you're using potions to remove a specific mutation, you can fail to remove that mutation, or introduce even worse ones in the process.
Therefore, you should treat potions of mutation as a 'semi-permanent' resource, and bad mutations as a 'semi-permanent' cost. Try to avoid malmutation at all possible - see the Malmutate article for more details how. Also, it is unadvised to drink potions in hopes of a good mutation: they are your only way of curing bad mutations, and it often takes multiple potions to get a tolerable mutation set.
- Prior to 0.28, Jiyva had the ability to Cure Bad Mutations. Its mutation gifting logic was also changed between versions.
- Prior to 0.21, random mutations could be obtained by eating mutagenic chunks.
- Prior to 0.20, there were potions of cure mutation and potions of beneficial mutation; regular potions of mutation gave random mutations and didn't remove any. Also, Zin offered a 1-time ability at 6* to cure every mutation you had (instead of cleansing mutation potions).
- Prior to 0.20, undead would sometimes rot instead of taking stat damage in place of mutations, and Mummies had a self-restoration ability.
- Prior to 0.18, there was an amulet of resist mutation, and rMut from the amulet or from artifacts gave a 90% chance to resist.
- Prior to 0.16, the Hat of the Alchemist did not grant mutation resistance.
- Prior to 0.15, vampires had differing responses to mutations at different satiation levels.
- Prior to 0.13, there were potions of gain strength, dexterity, and intelligence in place of the potion of beneficial mutation.
- Prior to 0.12, Polymorph Other (whether from a wand or the monster version of the spell) could inflict bad mutations on you. It was replaced by Malmutate.
- timed-effects.cc:105 (0.30.1)
The 4th property, "force_mutation", has its value set to coinflip - so it's a 50% chance to ignore all resistances.