Chess variant where White has lots of pawns, but nothing other (not even king), and Black has the usual set of pieces.
Black wins by capturing all white pawns. White wins in the usual way: by checkmating Black.
Otherwise the rules of chess apply, with the following difference:
Pawns on both sides can promote to any of the usual four pieces.
The number of white pawns can be changed.
Note: if White cannot move but has at least one pawn, the game draws by stalemate.