Proteus

From BoardGameGeek:

Taken from the website: From the folks who brought you Knightmare Chess comes Proteus - a dice game that plays a little like chess and a lot like nothing you've ever seen before! Played on a standard chess board, each side gets 8 dice, with a different piece on each face. You start with 8 pawns, but each turn you get to change one of your dice to a more powerful piece. But as your pieces get more powerful, they become worth more points to your opponent! The game is easy to learn, but mastering the intricate strategies will prove much harder.