Mutations change a character's body. They cannot be bought. A Heffith grows them with every experience level, and any character can be changed by a mutagen. The Mutations tab on the character sheet lists what has taken hold, and its tree shows what could come next.
A Heffith begins the run with one mutation already taken hold and grows one more with every experience level. Every other race changes only when something changes them, such as a mutagen, and their first mutation opens the Mutations tab.
Mutations grow in six lineages. A mutation can only appear once the one it grows from is carried, so each lineage runs from a faint first change to an unmistakable one. A lineage you already carry is three times as likely to be chosen as a new one.
A mutation can change attributes, Health, Mana, Melee, Ranged, Dodge, Sneak or carry weight, add elemental defence, grant a perk, teach a skill, add or take away Action Points in certain places, or stop the body wearing a kind of gear. A first change costs more than it gives, the middle of a lineage roughly breaks even, and only the deepest mutations pay off. A penalty never lowers a stat below 1, and a stat already at 1 is left alone.
When a mutation that blocks gear takes hold, anything you wear of that kind comes off, and nothing of that kind can be equipped while the mutation is carried. A cursed item stays on.
Some mutations change the Action Points of a turn by where it starts: in a flooded location, underground, or under open sky. A gain appears as green points past your usual maximum and is spent first. A loss appears as dim red points at the end of your bar. Several mutations add up, and a turn never has fewer than 1 Action Point.
Carrying mutations costs Comfort every turn: 1 for each tier carried, and 5 more for each lineage carried beyond the first. The Comfort breakdown lists both. Each tier 3 mutation also makes hunger come one turn sooner, up to two.
Every mutation other people can see lowers Charisma by at least 1, and a hidden one costs none. Charisma shapes how people react to you, and it never falls below 1.
A granted perk ignores the perk it would normally require, and it does not raise the price of the next perk you buy. A perk you already own is unchanged, and a perk closed off by one you have sworn to is not granted.
Long Fangs and Venom Glands teach Bite, and Talons and Wing Fingers teach Rend. Both are made with the body, so the weapon in your hand adds nothing to them and is not worn down, and the enemy must be next to you. Bite is one heavy blow at +3 damage and -5 Melee for 5 stamina, and a character with Venom Glands also leaves 2 acid damage in the wound for 3 turns. Rend rakes the same enemy twice at +1 damage and -10 Melee for 6 stamina, and only the second rake can draw a counter-attack. Both train Unarmed, and Martial Artist adds its unarmed bonus.
Some mutations reshape the body in ways that cannot coexist, such as webbed hands and wing fingers. Growing one closes the other off for the rest of the run, and closing off a lineage's first mutation closes the whole lineage.
A Heffith can spend experience to put down a mutation that has nothing grown out of it. The price is 100 XP per tier, doubled for every suppression already paid for. Its effects are removed, a perk it granted is lost though perks bought on top of it stay, a skill it taught is lost unless another mutation or a perk you hold also teaches it, and it never returns. Experience spent here is experience not spent reaching the next level.
Some cards can change whoever uses them. Blight fruit carries a 1% chance of a mutation, and when a character who already carries mutations is changed, one time in ten the change removes a mutation instead. Stabilized Arcane Vial carries a 10% chance and never removes one. A mutation removed this way costs nothing and can grow again later.
Gills, webbing and a body that would rather be under water.
Slick Hide
Your skin never fully dries. It turns the cold aside and slips out of a grip, and it leaves a damp mark on every seat you rise from.
Gill Slits
Four wet lines open along your throat. Water is where you move best now. Dry air leaves you short of breath.
Webbed Hands
Skin has grown between your fingers to the second knuckle. Your hands move water beautifully, draw a bowstring badly, and no glove will go over them.
Cannot be held with Wing Fingers
Deep Lungs
Your chest has rebuilt itself for pressure and stayed that way in open air. You are very hard to drown, and no breastplate closes around ribs this wide.
Lateral Line
A seam of raw nerve runs from jaw to hip and reads movement out of the air itself. You flinch before you know why, and the noise of it never lets your mind settle.
Nose, fangs and the long legs of something that runs its food down.
Wet Nose
Your nose has gone black and cold and it works far better than it used to. Rot, blood and fear arrive before you see their cause, and they are hard to put out of your mind.
Long Fangs
Your eye teeth have grown past your lip. Your bite is a real threat, your speech is not what it was, and patient work with a bow no longer comes naturally.
Digitigrade Legs
Your heels have lifted clear of the ground and you stand on the balls of your feet. You can run for miles, and no boot is shaped for a foot like this.
Killing Bite
The jaw has widened into a short muzzle and no helmet closes over it. With nothing in your hands you close on a throat the way a wolf does.
Cannot be held with Unhinging Jaw
Running Coat
Coarse grey hair covers you from the shoulder down. You can sleep in the cold, you think less like a person, and you cannot pass for one in daylight.
Light bones, a hunting eye, talons and wings.
Hollow Bones
Your skeleton has thinned from the inside. You carry less, you break more easily, and you move like something that expects to fall a long way.
Cannot be held with Plated Hide
Raptor Eye
Your pupils have gone hard and round and each eye tracks on its own. Distance means nothing to you, and anything close enough to touch is a blur.
Talons
Your toes have lengthened and curled and each ends in a hooked black nail. You grip stone and flesh alike, and you walk barefoot now whether you like it or not.
Nictitating Stare
A second lid sweeps sideways across each eye. Nothing gets into them, nothing makes you blink, and nobody holds your gaze for long.
Shoulder Wings
Two feathered wings have broken out between your shoulder blades. Under open sky they carry you further than your legs ever did. Below ground they drag and catch on every wall, and no armour will close over them.
Cannot be held with Wing Fingers
Heat pits, venom and a jaw that comes apart to swallow.
Forked Tongue
Your tongue has split and you have learned to taste the air with it. It reads a room well, it keeps flicking when you would rather it did not, and it ends most conversations early.
Venom Glands
Two sacs have grown behind your jaw and they are always full. Your own blood carries it, so what you spit and what bites you both matter less, and it slowly poisons you too.
Heat Pits
Shallow hollows have opened between your eyes and your nose, and they read warmth. Darkness stops being empty, and daylight becomes a glare you have to squint through.
Unhinging Jaw
Your jaw comes apart at the back. You can swallow things no mouth that shape should manage, and nobody watches you eat twice.
Cannot be held with Killing Bite
Shed Skin
Every so often you come out of yourself whole. What is underneath is new and heals quickly, and it stays stiff for days.
Ears, clicks and the thin stretched hands of a bat.
Leaf Ears
Your ears have grown tall and bare and they turn on their own. You hear a great deal, you cannot shut any of it out, and no helmet will sit over them.
Throat Clicks
You have started making a sound too high to hear and reading what comes back. Below ground you know the shape of a room before you enter it. In the open the echoes never return, and the clicking crowds out your own thoughts.
Wing Fingers
Three fingers on each hand have stretched to twice their length and thin skin has filled the gaps. Delicate work is easy. Gloves and shields are not.
Cannot be held with Webbed Hands, Shoulder Wings
Echo Map
The clicking never stops now, awake or asleep. You know where everything in the dark is moving, and you have almost stopped sleeping.
Blood Thirst
Warm blood has become food to you, and it agrees with you more than bread does. You are stronger for it, and quicker to anger.
Plate, horn, cold blood and a tail.
Scute Patches
Hard overlapping plates have come up along your forearms and shins. They turn a blade aside, they clack when you move, and they do not bend when you need them to.
Plated Hide
The plating has closed over your back and ribs. You can take a great deal now, you turn slowly, and you carry all of it everywhere.
Cannot be held with Hollow Bones
Cold Blood
Your warmth now comes from outside you. You bask where others would sweat, you are harder to hurry, and slower to move when it matters.
Horned Crest
Horns have grown up out of your skull and a ridge of bone runs down your spine. Very little gets through you, and no helmet made for a person will go on.
Lashing Tail
A thick scaled tail has grown from the base of your spine. It balances you and it hits hard, and no pair of leggings was ever cut for it.