Deltapack is THE deltarune datapack that you have been searching for!
Whilst currently small it features a decent amount of content to kickstart your deltarune journey.
The Knife: Craft a knife then stab the ground to open a dark fountain, will convert nearby items into a darkner.
Snowgrave: Well that took a weird route, craft snowgrave and use the spell to freeze all nearby entities to death....
The Roaring Knight: The first (and currently only) boss! A difficult bullet hell styled fight where they attack first, then you get a chance to attack, mimicing the turn based combat of the original game.
The Shadow Mantle: Greatly reduces damage from firework and magic attacks, which happen to be the exact kind of attacks The Knight uses.
The Shadow Crystal: Drops from the Roaring Knight, consume it to gain their abilities!
deltarune by toby fox this is not afilliated with toby fox or deltarune, it is simply a fan creation (ive never played deltarune so mb if its inaccurate i make this stuff for fun)