Puzzle Piece (Mario + Rabbids Kingdom Battle)
From the Super Mario Wiki
Puzzle Pieces are collectibles in Mario + Rabbids Kingdom Battle, found exclusively in the Donkey Kong Adventure mode. They are items that are found in the overworld that, when collected, fill up a jigsaw puzzle on the hub isle. Once all pieces are collected, the jigsaw collapses and serves as a bridge to the treasure chests containing the First Class Crusader, Golden Gyre, and Honey Hurler.