The ubi-ubi is a less well-known fairy chess problem piece. The only game I know of that uses this piece is Ubi-Ubi Chess, game considered unsuccessful by its inventors. Ubi-ubi means 'everywhere' in Latin.
The ubi-ubi makes an arbitrary finite number of knight moves in a single turn as desired. It must stop when it captures an opponent's piece.
The ubi-ubi is a powerful piece; on an empty board it can, of course, reach every square on the board.