Mutagen: Evolve

v0.1 - First Dose

First public release. Mutagen adds a transformation that takes time: you hunt a mob, take a tissue sample, read its genome in the lab, synthesize a serum — and then keep dosing yourself for in-game days while your body rearranges itself, bone by bone, until you are no longer rendered as a player at all.

Two rules the whole mod is built on:

• A dose does not raise your progress. It fills an absorption reserve that the body works through slowly, and without a supporting dose the transformation falls back on its own.
• Every ability ships with its price in the same version. Not later, not in a balance pass.

Added

Gathering

• Syringe — right-click a mob to take a tissue sample. The mob takes a point of damage, turns on you, and will not give a second sample for ten in-game minutes.
• Sample purity (5–100%) — a target below 30% health gives better material (+15), so does an adult (+10) and one that is asleep, riding, leashed or heavily slowed (+10); a baby gives almost nothing (−20). A mob from a spawner or a trial spawner is an exhausted line (−30). Purity carries through the whole chain and decides how strong the final dose is.
• Golden syringe (+10 purity, 32 uses) and netherite syringe (+25 purity, 128 uses) are not spent on every sample the way the iron one is.
• Samples, genomes and serums each carry their strain and purity, visible in the tooltip.

The lab

• Bio Workbench with its own recipe type, mutagen:bio_workbench: ingredients with counts, no shape. Everything the lab needs is made here and only here. A recipe list beside the grid shows every assembly, highlights the ones you can already make, and lays a recipe out from your inventory on click.
• Centrifuge — burns ordinary furnace fuel and turns a raw sample into a purified genome in 10 seconds. Purification recovers part of the lost purity but never all of it.
• Sequencer — spends a raw sample and redstone dust over 20 seconds and adds research of that species.
• Synthesizer — genome + mutagen base + catalyst → serum. The cost comes from the strain: a zombie takes 1 catalyst and 15 s, a skeleton 1 and 20 s, a creeper 2 and 25 s. A genome of 85% purity or more yields two ampoules instead of one.
• Machines say why they are idle — missing research, the wrong catalyst, not enough of it — and what the result will be: the serum's cap and how many ampoules it gives.
• Machines keep their contents, drop them when broken, and show progress on screen.

Knowledge

• Research thresholds. 25% — the gene list becomes readable and a weak serum can be made, capped at 40% progress. 50% — full serum, capped at 70%. 75% — the serum leads all the way to the full form. 100% — the strain holds without a stabilizer and stops decaying.
• A serum carries its own cap, shown in the tooltip. A dose never fills the reserve past it, and a serum that cannot take you further is refused before the injection, so the ampoule is not wasted.
• Research belongs to the world by default, so a team researches together. With knowledgeScope: "player" everyone keeps their own and a machine works for whoever opened it last.
• Gene tree on G — a catalogue of every species you have sampled: the creature turning to follow the mouse, its difficulty, research with the thresholds marked, the full-form hitbox, eyes and reach, and its genes: abilities in green, weaknesses in red, each with the stage it starts at.

Strains in datapacks

• A strain is a JSON file in data/<namespace>/mutagen/strains/<name>.json: the creature, colour, difficulty, synthesis cost, body description and a list of traits. The three built-in strains ship as such files and can be overridden.
• Trait types: attribute, effect_immunity, damage_factor, dark_regeneration, sun_burn, cat_fear, armor_rejection, arrow_power, no_offhand, inventory_limit, no_tools, no_crafting, no_building, no_sleep, diet, no_eating. A stage may be written as a word ("mutation"), a Roman numeral ("III") or a number (3).
• /reload works on a running server: strains are re-read, sent to every client and everyone's traits are rebuilt at once. A broken file never stops the rest from loading, and operators are told what loaded and what was skipped and why. Genes of a removed strain stay in the save and go quiet until the file comes back.
• A strain from a foreign datapack without a translation is named after its creature — "Witch Strain" — instead of showing a raw key.

Transformation

• Absorption reserve — a dose is stored in the body and absorbed at 1% every 30 seconds.
• Decay — without a supporting dose progress falls by 1% every 8 in-game minutes. The full form is the exception: once the body has turned completely there is nothing human left to pull it back, and only a reversal serum will.
• Five stages — Infection (1%), Manifestation (21%), Mutation (41%), Domination (71%), Full Form (100%).
• Transitions are events — a sound, a screen flash in the strain's colour, a line in chat, and a convulsion that wrenches the body for a couple of seconds, visible to everyone watching.
• Stabilizer locks the current level so it stops decaying; used again, it releases the lock.
• Reversal serum rolls the transformation back 15% per dose, with nausea, weakness and damage. Milk does not remove a strain, and that is deliberate.
• State lives on the player, is saved with the world, and survives death, respawn and relog. It carries a data format version from this first release, because the 2.0 world converter will need it.
• State is sent in compact binary deltas, and only when something visible changed: 0.1% of progress for your own HUD, 1% or a stage change for everyone else, who only need the body.

The body turns

• The infection spreads in patches. From stage II the skin no longer takes an even tint. Patches of the creature's flesh appear where the needle went in and spread bone by bone — a zombie strain starts at the right arm, a creeper strain at the head. Every bone has its own window of progress and the windows overlap, so an arm is almost foreign while the infection is only reaching the feet. Each carrier's pattern is their own, seeded from their UUID and identical on every client.
• The edge of a patch is darker, like inflamed skin around a wound. Where the creature's texture shares the player's layout the patches are its real hide; otherwise they take the strain's colour, mottled. Your own skin shows through until the last stage — at most 86% of it is taken before the full form.
• The model itself changes shape. Nothing is laid over the player: every bone — head, body, arms, legs — takes the size, position and rest angle of its counterpart in the creature's real model, in step with the infection of that bone. A skeleton's limbs thin down to bones; a creeper's legs shorten to stubs and its body sinks onto them, feet always on the ground.
• Every limb has somewhere to go: a creeper's arms become front legs, the player's legs the hind ones. Bones can be absorbed when the creature has fewer, and parts the player does not have can grow out and travel with a chosen bone.
• Clothes come off: the second skin layer falls away from a bone once it is half turned, so the hide and the patches never form a double skin. A fully turned bone gives way to the creature's part completely, gaps included — a skeleton's ribs become see-through.
• The rebuild happens like a body, not like an animation. A limb first sinks and slides down along the side, and only then moves forward or back and tucks under the torso. A bone thickens or thins before it changes length, swells and trembles while it changes, and settles when it is done. An arm that became a leg walks like one, in step with the leg across from it, and no longer draws what it was holding.
• Twitches. From stage III a bone jerks on its own every few seconds; at stage IV more often and harder. Each carrier has their own rhythm.
• Full form replaces the model with the creature's own, drawn through the vanilla mob renderer, with its animations and layers, your armour and held item on it, and your name still above you on a server. By 100% the player's model already has the creature's shape, so this is the last step and not a jump.
• First person follows: once the hybrid has grown the creature's arm, you see that arm.
• Real dimensions. Width, height and eye height move towards the creature's own values independently. By default these are its real in-game dimensions: a creeper is 1.70 tall with eyes at 1.445, a zombie 1.95 with eyes at 1.74, a skeleton 1.99. Reach changes too: +0.5 for the zombie's long arms, −0.5 for the creeper. Crouching, swimming and every other pose keep vanilla proportions on the new body.
• Works for any mob with a vanilla model layer, datapack strains included: without a list of parts, bones are matched by name (head, body, right_arm…).

A body without hands

• A creeper has nothing to hold things with, and the carrier loses it step by step:
  • stage III — the second hand is gone; whatever it held falls into the inventory;
  • stage IV — the pack is out of reach and five belt slots are left; tools and weapons cannot be held; crafting stations and the inventory grid need fingers the body no longer has;
  • stage V — three belt slots; blocks can no longer be placed. Chests, doors and levers still work.
• Items in locked slots are never lost: they stay put and come back with the hands. Picked-up items only go where the carrier can still reach. Locked slots are shaded and struck through everywhere, and every refusal explains itself above the hotbar. The lab itself stays usable, so there is always a way back.
• The other strains pay too. A zombie stops sleeping at III; at IV it eats only meat and rot and loses fine work — enchanting, anvils, smithing, brewing. A skeleton stops sleeping at III; at IV it has nothing to digest with and cannot eat, but does not starve either — hunger stands still at 17, just below natural healing; at V its bony fingers lose fine work as well.
• All of it turns off with humanityPenalties.

Strains in this build

• Zombie — undead strength, regeneration in darkness, extra health, immunity to Hunger. Price: slower, burns in sunlight, stops sleeping, eats only meat and rot, loses fine work.
• Skeleton — poison and hunger do nothing, arrows hit 1.5× harder. Price: brittle, blasts hurt more, burns in sunlight, cannot eat at all, loses fine work.
• Creeper — immune to blasts, quick and quiet. Price: panics near cats, nothing to strike with, vulnerable to fire, and loses its hands entirely.

Compatibility

• Pehkui — recommended, never required. With it the body changes through Pehkui's own scale types: hitbox width and height, block and entity reach, inertia. Mutagen keeps Pehkui's model scales at 1 (the model already has the creature's shape) and corrects eye height to the creature's own. It is reached only through a small bridge and reflection, so the mod builds and runs without it and falls back to vanilla scaling instead of crashing if the API changes. Pehkui scales are not saved on the player: remove Mutagen and you are human-sized again.
• Iris and Oculus — mutation overlays skip the shadow pass of shader packs, where they only added dark halos.
• Sodium and Embeddium need nothing special: every layer is drawn through vanilla model parts.
• A compatibility report in the log at startup lists which known mods were found and how Mutagen behaves with each; /mutagen status shows which scaling is in use.

Control and project

• /mutagen (permission level 2) — status, list, dose, set, lock, clear, research. Strain ids accept both mutagen:zombie and the short zombie.
• HUD indicator — strain, stage, a progress bar with the unabsorbed reserve behind it, a lock marker. Exact numbers on the F3 screen.
• 14 config keys, including hybridRender, bodyMorph and bodyMotion to turn the body changes off if they clash with another model mod.
• Hand-drawn textures for every item and lab block: syringes with glass barrels and metal plungers, labelled ampoules, round-bottom flasks, and machines in a shared casing with a rotor behind glass, a liquid chamber and a DNA screen.
• Seven languages: English, Russian, Ukrainian, Polish, German, French, Spanish.