Ooh, I like it. But let's not just give it to the opponent. You don't get to know the outcome of the roll. They cover the die each time. If the opponent's roll is successful, the piece becomes a double agent. You can still promote and move the piece, attack with the piece, but at any time, your opponent can uncover the die, use the piece to make one attack, and then remove it from the board.

If your piece is compromised and checks your own king, you lose.