It's a mod that adds new features to Happy Ghast entities.
It started as a simple mod that added a small tweak to the game. You can still find the original version on GitHub, in the v1 branch.

Requires Fabric API to work

Must be installed on both client and server

2 New Harness Types

Adventurer's Harness

Equipped with a crafting table, a chest, a furnace and a bed(not implemented yet)

Demolition Harness

Equipped with 4 powerful dispensers, they can carry every payload you want! (i prefer 2304 tnts)

Press the keybind(default is R) to fire them