Deltatale Bosses V1

Undertale's biggest bosses have turned up in Deltarune Chapter 5.

You start in the Boss Hall. It's a golden, Judgment Hall-style room where Toriel, Papyrus, Undyne, Asgore, Mettaton and Sans stand in a row while Snowdin's town theme plays. Walk up to anyone and press Z to fight them.

Deltarune designs. Toriel, Sans, Undyne and Asgore look the way they do in Deltarune, read from your own Chapter 5. Papyrus and Mettaton aren't in Deltarune, so they use their Undertale sprites.

Your real party (F6 → Party). Kris leads. Choose who joins him from Susie, Ralsei and Noelle. They are the game's own party members, with their real stats, spells, ACTs and battle HUD.

Six boss fights run in Chapter 5's battle system, each with the boss's own music, attacks and ACTs:

• Toriel: fire rain and sweeping fire (Heartache)
• Papyrus: bone walls and blue bones (Bonetrousle)
• Undyne: lock-on spears and a closing spear ring (Spear of Justice)
• Mettaton: stage blocks and tumbling boxes
• Asgore: fire rings and blue/orange trident sweeps
• Sans: bones and Gaster Blasters (Megalovania). He dodges until he's tired.

You can spare them, Pacify them, or beat them.

F6 menu: Boss Hall, Party, Fight Sans now, and Go back where I was (which takes you to Chapter 5's normal start).

Good to know: you need Deltarune (the full Steam release) and Undertale (PC). The mod plays Chapter 5. Your installs are never changed: the mod builds its own patched copy of Chapter 5 and keeps its own save folder, started from a copy of your Chapter 5 saves. Single player.

Built with Claude using the universal-modder toolkit, and patched with UndertaleModTool (GPL-3.0, bundled unmodified).