haven't been to fossil island yet... might give it a go especially since they've buffed it
this deadman mode clarification seems pretty cool:
"When we reach 200 players, we’ll be transporting them to a new, Deadman-only archipelago, where they’ll be divided randomly between four islands. On each island, players must fight to the death until just one player remains. The surviving four players will then be brought to the final island, to engage in two 1v1 fights, and a final 1v1 fight to decide the winner. Tournament only"