Corruption: The Withernder

An addon for [Corruption] that turns the mod into a story with an ending.

Using the bone meal a spent Relic of Purity leaves behind calls down The Withernder — a three-formed boss born from the corruption. Kill it and the heavenly scourge is over for good.

How to start the fight

1. Craft a Relic of Purity and use it on corrupted obsidian until it is spent (three uses).
2. The spent relic turns into a bone meal — its residue.
3. Use that bone meal anywhere. Something immense answers.

Only that residue works — ordinary bone meal does nothing. Only one Withernder can be awake in a world at a time, and once the corruption has been cleansed the residue is powerless.

The Withernder

It is a corrupted cousin of the warden, and it looks the part: it uses the warden's own body, rig and animations.

It fights in three forms, evolving at 50% and 10% health:

• Form I — the bone husk (100–50%) — a closed bone shell over the whole body: shoulder, chest and limb plates with a mask over the face and whole horns. Souls glow dimly through the seams of its sealed ribcage. Quiet and armoured (+8 armour).
• Form II — shadowed and cracked (50–10%) — the plates are holed and cracked, the horns are broken off at the tips, and withering energy bleeds out of the split chest with veins running across the body. It moves 1.12x faster, hits 20% harder, every claw hit withers you, and it starts calling wither skeletons to its side. Its claws lift into a fighting stance.
• Form III — full corruption (10–0%) — the horns are gone entirely, only shards of the shell remain and the chest is torn open into a bright void maw of souls. It loses all armour but hits 50% harder, grows to 1.28x (about 3.7 blocks) and keeps releasing a corruption pulse: everything within 9 blocks takes damage and gets Darkness, Slowness and Wither. The boss bar turns blue and world fog closes in.

The form art is drawn for this addon as two layers over the body — a matte bone shell and an emissive pass for the souls, the withering energy and the void maw.

Each evolution changes its colour, size, bar colour and name, and tells nearby players which form it has taken.

The finale

When the Withernder dies, everyone on the server is told:

You have withstood the heavenly scourge. The corruption recedes — no new corrupted obsidian will appear and everything it already claimed is evaporating.

And it really happens:

• corrupted obsidian stops appearing near players,
• it stops spreading — corrupted blocks left in the world evaporate instead,
• everything the corruption already claimed is removed, sweeping through loaded chunks a couple of chunks per tick (no lag spikes) and cleaning chunks as they load later,
• the state is saved with the world, so the corruption stays gone after a restart.

Requirements

• Minecraft 1.21.1
• NeoForge 21.1.0 or newer
• Corruption 1.0.9 or newer (required — this addon uses the purification API and the residue marker added in that release)
• Java 21
• Environment: client and server (on a server it must be installed together with Corruption)

Notes

• Spawn egg: a Withernder spawn egg is available in the Spawn Eggs creative tab (handy for testing).
• The boss is drawn with the game's own warden model, skin and animations — they are referenced at runtime and are not copied into this mod. The only texture shipped here is the corruption glow overlay, made for this addon.

Credits

• Original Corruption mod, design and gameplay: MBP — <link to the original CurseForge project>
• This addon (boss, art, finale logic): <your name or handle>

This is an unofficial addon made with the original author's MIT-licensed work. If you are the original author and want it changed or taken down, contact me and I will do it immediately.