The Ubi-ubi is a rather strong fairy chess piece, and we wondered how this piece would do in a chess variant. The first variant tried was dismissed as `not good' after a little experimentation - a correction was not tried anymore. I'm told that ubi-ubi means `everywhere' in Latin.
King e1; Queen d1; Rook a1, h1; Ubi-ubi b1, g1; Bishop c1, f1; Pawn a2, b2, c2, d3, e2, f3, g2, h2.
King e8; Queen d8; Rook a8, h8; Ubi-ubi b8, g8; Bishop c8, f8; Pawn a7, b7, c7, d6, e7, f6, g7, h7.
Ubi-ubi's can make arbitrary (but not infinitely) many knight moves, but must stop their movement when they take a piece from the opponent.
Unfortunately, the game is flawed: after a little experimentation, it seems that the best white can do is to exchange all four ubi-ubi's, after which he has a better position in an otherwise further normal game of chess. If white does not exchange ubi-ubi's, then black should do so, while playing h3 is deadly for white.
Now exchanging knights/ubi-ubi's would be disadvantageous, as the player whose piece is taken would determine the other `knight' to be the ubi-ubi.