Geo is a currency in AUT. It originated from the popular platformer "Hollow Knight". It cannot currently be used, but shops will open in the future.
Geo is dropped by Primal Aspids. There are three possible sizes; the small gives one Geo, the medium gives five Geo, and the largest gives 9-10 Geo. Note that the knight does not need to be equipped to collect Geo. Geo is kept even if you leave the game, similar to Stacks.
Geo are used to upgrade The Knight. Geo count can be seen while the knight is equipped.