Delta Bros

Sans takes Kris's place in Deltarune Chapter 1, and Papyrus takes Susie's. Both are built from your own copy of Undertale, along with their faces, voices, fonts, bones, Gaster Blasters and MEGALOVANIA.

The skeleton brothers

• Sans replaces Kris and Papyrus replaces Susie, in the Light World and the Dark World: walking, cutscenes, battles, the party panel and dialogue faces.
• Everyone reacts to the brothers. About 580 lines are rewritten. Sans finally talks back in his Comic Sans, and Papyrus speaks in his own font and voice, IN CAPS.
• Sans: 1 HP, 31 dodges per fight. Every hit aimed at him is a MISS until the dodges run out. After that, one hit and it's game over.
• Papyrus: 120 HP. He takes his own hits like any party member.
• The soul is white and upside down, and SPACE dashes it through bullets.

Sans's moves

• Bone Barrage, Gaster Blaster (three of them), Bone Zone, Blue Soul and the Gaster Blaster Circle.
• KARMA keeps draining HP, scaling with his MAGIC.

Papyrus's moves

• Bone Toss and Blue Attack (jump the bones!).
• Bone Wall: find the gap!
• COOL DUDE Special.

When the brothers attack, the fight flips: every enemy's soul drops into one box and tries to dodge. Damage only lands when a bone or beam actually hits.

Also

• MEGALOVANIA on every boss and "sans." in town.
• Both brothers have a line for every battle action.
• DeltaSans uses its own save slots, so your Kris saves stay untouched.

Solo. Needs Deltarune and Undertale (PC). Nothing from either game is included: the mod reads your installed copies, and your original files are never changed.

Credits: Deltarune and Undertale by Toby Fox. UndertaleModLib by the UndertaleModTool contributors (GPL-3.0). Source included (GPL-3.0); remixes welcome.