Mutation

Mutations act much like traits, in that they give your character a variety of passive effects. Unlike traits, which can be selected upon creating a new character, most mutations can only be obtained in-game and are somewhat random. Like traits, mutations can be both beneficial and harmful to your character.

Does it hurt?

Repository of mutation graphs, PNG and SVG version

Yeah, sometimes. Mutations can be obtained by consuming some questionable products (mutagens, mutagenic serums, misshapen fetuses, arms, and legs), and romping through radioactive areas, among other methods. Any time you mutate, you have a 2/3 chance to get any type of mutation and a 1/3 chance to get a "bad" mutation, though not all "bad" mutations are truly bad ones and not all "good" mutations are equally desirable. The Robust Genetics trait improves your chances of getting a "good" mutation. For the spoiled, Robust Genetics works by changing the 1/3 chance to receive a "bad" mutation to a 1/3 chance to receive a "good" mutation.

If you end up with unwanted mutations, a purifier can purge them. It can revert up to four mutations, with the higher end being reached by heavily-mutated characters. However, not all mutations are purifiable; additionally, purifier won't remove any starting traits, positive or negative, that you selected when building your character. In addition, which mutations (normal) purifier removes are random.

Even if there is no forced "bad" mutation, chances are not equal for all traits. Mutations are split up into a dozen categories and even more trees. Trees have various requirements for the different branches and most branches are opposed to one another. The more branches are opened up, the less likely a new branch or a categorized mutation will be gained, with the game prioritizing current upgrades to everything else. Direct upgrades have the most priority, with a (5/(number of available upgrades + 5)) chance to be skipped, then mutations from a category pool, and only then does the game pick random mutations from the full list of all mutations.

Once the code determines what trait you're due to get (generally based on mutation category, either your strongest one or what you opted to use), it then starts mutating you in that direction. Since it can pick traits for which you haven't got the prerequisites, the code will then downshift and give you the most relevant trait you can obtain.

For example, if TRAIT_$LETTER needs the preceding letter (B needs A, C needs B, and so on) and the code goes for C, it'll give you C if you have B, B if you have A, and A if you don't have any of them. If you used something that gives more than one mutation in one go, there's no guarantee that the next mutation will then continue the chain. Sometimes it happens. Sometimes it doesn't—that's how mutations work!

Cost

While most mutations are passive and are thus constantly in effect or conditionally triggered, a small number manifest as active abilities and can kick in on demand; some will self-trigger by random chance. Like bionics, player-initiated use of these mutations has a use cost, and most of them add their corresponding cost(s) to your hunger, thirst or fatigue level. At certain caps, however, the action will instead be canceled (or interrupted), such that you cannot kill yourself by using your mutations. Hunger caps at 44000 stored kcal (where you start getting messages), thirst at 260 (a bit over Dehydrated), and fatigue at 400 (a bit into "Dead Tired").

To access the mutations menu, which can be used to toggle mutations or activate them, use the [ key by default.

Categories

Traits tend to provoke other mutations from the same category—your genetic and biochemical makeup is shifting.

When you mutate, the game checks your mutations and notes which category is most strongly represented. If no single category is the strongest, a completely random mutation will be chosen, thus not necessarily one of the strongest categories. The strength of a category is increased by having mutations of that category, and by having mutations that are linked to mutations of that category. A matching category is worth 8 points, halving with each link. So for example, Ugly gives 8 points towards Feline because it is a Feline mutation, and it gives an additional 4 points towards Feline because it is linked to Deformed which is also a Feline mutation. "Linked" in this case only refers to "Requires", "Additional Requirement", and "Changes Into".

Once a category is selected, you will mutate towards a random mutation in that category. A mutation that causes you to lose a mutation you already have is more likely to be chosen this way than a mutation that will simply be gained. For example, if your strongest category is Feline and you are Ugly, you are more likely to have Ugly turn into Deformed than to gain any other random Feline trait.

Once a mutation is selected, you will begin to mutate towards it. If any mutations you currently have conflict with this mutation, then one of the conflicting mutations is randomly removed. If you have no conflicting mutations, but don't have any of the prerequisites, you will begin to mutate towards a random prerequisite. If you already have a prerequisite mutation and no conflicting mutations, you gain the selected mutation immediately.

There are quite a few different categories, each providing a different type of experience when mutated into:

• Lizard: A tanky mutant with heat vision that heals quickly and needs little food, but is very slow in cold weather.
• Batrachian: Amphibious carnivore. Slow in cold weather, but has good battlefield control with its leaping abilities and ranged pull attacks.
• Gastropod: Saprovore. A slow-moving controller that relies on its sludge fields and range pull attacks to manipulate the battlefield. Good resistances.
• Rabbit: Can survive off of grass and has incredible stamina. Poor offense, but great dodge and a leap ability.
• Bird: The king of mobility thanks to its high move speed. Very fragile, but comes with very powerful beak and talon attacks.
• Fish: Has one of the best bite attacks in the game and offers top-tier dex. Great in water, but does well on land as long as it has enough to drink.
• Beast: Carnivore. Incredible strength and stamina. Poor stealth, but lots of natural attacks. Needs a lot of meat to survive, but it's worth it.
• Feline: Carnivore. Focuses on dexterity, dodge, and stealth. Gets parkour for free and has a leap attack for getting in/out of trouble. Doesn't mind the cold.
• Lupine: Carnivore. Amazing stamina, high strength, fast movement. Poor stealth due to its tendency to howl, but great at intimidating NPCs. Loves the cold.
• Ursine: Incredible melee tank. Doesn't do well in the heat, but has enormous HP values and gets to remain an omnivore.
• Cattle: Both the chillest mutant and one of the most powerful. Some of the highest HP and strength values, great natural attacks, huge, literally just eats grass from outside.
• Insect: Very chaotic category with lots of ups and downs. Acidproof, fast, and well-armored, but can sometimes get stuck with a liquid diet.
• Plant: Mostly eats sunlight, but also needs rotten food. Very slow, but immune to disease, super tanky, and quite strong. Basically an ent from Lord of the Rings.
• Slime: Regenerating liquid super-genius that occasionally asexually reproduces and is immune to almost everything except physical attacks.
• Troglobite: A super-strong regenerating disease-ignoring infection-resistant CHUD that can eat trash and only one downside: they can't stand sunlight.
• Cephalopod: A superintelligent highly dexterous melee tank. Bad at using guns and grenades, great at almost everything else. Loves water, gets thirsty on land.
• Spider: Grows its own incredibly powerful armor, is very very fast, has a poison bite, and spins webs that tie enemies up.
• Rat: Gain resistance to most disease, infection, etc. and some natural attacks. The main draw is the ability to eat zombies, and the only real downside is that it's always hungry.
• Mouse: Become the size of a garden gnome and gain Ultra Instinct style dodging. Fantastic at melee thanks to its near-infinite stamina, but needs lots of snacks and naps.
• Medical: Basically a cenobite from Hellraiser. Doesn't alter the body or your diet, gives the best resistances and HP, comes with fast healing. Either immune to pain or in love with it. Also: completely insane.
• Alpha: The next stage in human evolution, and fairly low-impact. A born leader, beautiful, all stats get buffed, turns into an uptight prick and sometimes disintegrates if they take too much mutagen.
• Elf-A: Similar to Alpha, but with some plant traits. Emotionally unstable, but they almost never need to sleep and are the most beautiful mutant.
• Chimera: Absolutely the most powerful mutant in almost every respect, however they are almost always hungry. Once you go this route, you start killing and eating anything that gets in your way. You stop, you die.
• Raptor: Similar to bird, but it becomes a carnivore and is more durable in melee. Is also really good with guns thanks to high stats, IR vision, and a lack of hand mutations.
• Mycus: Play around with fungus to get this. You are now part of the fungal invasion of earth. Traitor!. Not obtainable using normal mutagens. Locks you out of other mutations.

For a complete overview, see List of mutations.

Thresholds

Though most mutations are more or less surface-only (and can be reversed with purifier), they do affect you whilst they're present. If you use particularly strong doses of targeted mutagen and are already strongly involved in that category, you may permanently transcend your humanity. This is known as "crossing the threshold". Becoming post-human unlocks further mutations which offer radical alterations to your character's body and mindset. At this point, the only disadvantage to crossing a threshold is that it bars you from crossing others.

Thresholds under the hood

You can only cross a threshold with injectable serums. No matter how many gallons you drink, drinking mutagen won't do the job. (That may change later, but it's not a major priority.) In order to be eligible to obtain a threshold mutation, the character must:

• Not have any threshold mutations (denoted by the threshold boolean set true in mutations.json, and currently all designated THRESH_$CATEGORY for clear reference/sorting)

• Have reached third-tier mutation dreams (they occur often and are fairly specific)

At this point, you need to be injecting mutagen specific to your strongest category. If you dream of chasing rats, for instance, you're third-stage Feline. If you meet the above criteria, injecting Feline serum will have the usual effects, and then roll to see if you breach the threshold.

The roll is a straight "x in y" roll: your strength in your chosen category over your strength in ALL categories. If, to continue the example, you really wanna be a cat and use exclusively Feline mutagens, two or three injections, if you get all three mutations from each, might do the job. If you spread your mutations around and try different categories, it'll take more effort and more mutagen to breach a threshold.

Certain messages come up related to thresholds.

• "You feel something straining deep inside you, yearning to be free" indicates that the mutation process tried to give you a post-threshold mutation, but you didn't have the threshold required. Your humanity is resisting!

• The various headaches that can come up happen when you're particularly strong in a category and tried for a threshold, but you missed the roll. Your humanity resisted turning into a mutant creature!

Addiction

Mutating can feel good. It can make you feel great... smarter... more aggressive, as if you could TAKE ON THE WORLD.

As such, they can be quite addictive. Purifier can be more addictive; serums, being concentrated, are even worse.

Please enjoy responsibly.

Sources of mutation

Here are various ways you can get mutated after character creation. Some mutations are only obtainable on character creation, these are listed on the wiki as "Not a valid random mutation" in the mutation information box. Any others can be acquired via mutations, some might require special items the marloss mutations, or special serums, for the Threshold mutations.

• Mutagen
• Mutagenic and flavored serums
• Misshapen fetus
• Mutated arm
• Mutated leg
• Sewage sample (obsoleted)
• Sewer brew (obsoleted)
• Tainted tornado (obsoleted)
• Congealed blood
• Putrid heart
• Seeping heart
• Radiation
• Ratting (obsoleted)
• The activated and passive effects of certain artifacts
• A high duration effect of teleglow
• Through the Genetic Chaos, Genetically Unstable, and Genetic Downward Spiral traits.
• The special attacks of Yuggs

Targeted mutations

Not all mutations are valid mutation targets when being mutated. Some can only be chosen at character generation, and others require a specific threshold. Others cannot be randomly mutated at all, these will be listed as 'Targeted Mutation Only' on their mutation pages. This means you can only get them from mutation sources that have this mutation in their threshold list. For example, you cannot get schizophrenic from normal mutagen, but you can get it from medical mutagen.

If a mutation source can give you a mutation, then it can also give you the prerequisite mutations. For example, because medical mutagen can mutate Deadened, then it can also give you Pain Resistant, a prerequisite mutation.

As of 0.E (Ellison) there are no sources of mutation which will always give you a specific mutation. The mutations are always random, but special mutagen groups allow you higher chances of getting a mutation from a those lists of mutations. (But nothing is ever guaranteed.)

Phenotype/Instability

(0.G and above)

Mutating now creates a vitamin called "instability", which raises your rate of getting negative mutations. It goes down with time. With no instability, you are almost guaranteed good mutations. This also means that with too much instability, you are almost guaranteed bad mutations.

Every time you mutate, you gain a type of vitamin called "instability". This goes down over time naturally. Robust Genetics doubles the rate in which it goes down, while Genetic Downward Spiral causes it to increases over time. It has three stages of intensity:

Spent Phenotype: "Mutation has left you with a persistent mild discomfort. It seems harmless for now, but you can't predict if it'll get worse." (At this point, you can start receiving bad mutations.)

Depleted Phenotype: "There's an enervating sense of dysmorphia throughout your whole body. It waxes and wanes, but never quite goes away. Mutating this much can't be good for you…"

Bankrupt Phenotype: "You're haunted by phantom pains across your entire body now. Everything aches from an exhaustion that never seems to fade. Any further mutation right now is very unlikely to have a happy ending." (At this point, your odds of getting a bad mutation is equal to/exceeds your odds of getting a good mutation.)

See also

• Traits
• List_of_mutations0-F
• Extra attacks from mutations