the 4 leaf clover is a UNSC destroyer in the naval blocade. the destroyer was in very many battles and stayed in one piece.(probally why they call it the 4 leaf clover) though, in 2541, she was dispatched to negioate a peace treaty with the protogravemind,the soon to be leader of the flood, when the destroyer reached its destination, a flood proto-missile shot out the "mouth" of the flood form, destroying the ship almost in stantly, the flood shots departed from the ship to make it look like the covenant destroyed the ship.