Small summary explanation of the variant:

If a piece takes a piece it can move like that piece for one move. Powers dont add up. When a knight takes bishop, it can move and take ONCE like a bishop, even if the piece moves like a knight in between or if other pieces move. If that knight that just took a bishop takes a pawn, it now only has the extra powers of the pawn. It's now only a pawnknight. Taking the same piece twice will not grant you the right to use a power twice. That pawnknight, the knight that just took a pawn can now also promote (and stay that piece) and take en passant. Also kings can promote. They stay king but they can for example just move like a queen forever. The threat of using the power is not using your power. If a bishopknight goes to a square, a bishop-lenth away from the king, for example if the knight with bishop powers goes to h5, while black's king is on e8, it's check, and the bishopknight can still move like a bishop for once. You have only used your power if you have moved or taken like that power.