Chess, trolled: cards that decide your turn, knights that fuse with other pieces, or both.
Normal chess moves. Before every turn you draw a card from a shared deck, and the card is your turn.
Winning. Capture the enemy king, or checkmate it: if a player draws a number card while in check and has no legal move, they lose. A player left in check who draws Skip, Reverse, Draw 2 or Wild cannot answer it, and the king can simply be taken next turn.
Check ends your turn. A move that puts the enemy king in check uses up the rest of a 2 or 3, so the opponent always gets a card to answer with. You may end a 2 or 3 early after one move. With no legal move and no check, the turn just passes.
The deck is 40 cards and reshuffles when it runs out. A captured piece that had been promoted comes back as a pawn. Castling, en passant and promotion work as usual; a king or rook that was revived or moved by a Wild loses its castling right.
Three modes. Card Chess is the cards above with ordinary pieces. Fusion Chess has no cards: one move a turn with the fusion pieces below; checkmate wins as in chess, and 50 moves each with no capture and no pawn move is a draw. Card + Fusion (the default) is both at once.
Captured, a Knook or Knishop goes back to the pool as its two pieces. Draw 2 can revive a knight onto your rook or bishop in the revive quarter, or onto your king wherever it is: the one way a Draw 2 can shield a king in check. Wild can drop a knight onto your rook, bishop or king anywhere. Neither may put the enemy king in check. A pawn placed by a Wild next to an enemy pawn on the same rank can be taken en passant on the next move.