Mirrodin

Quicksilver Fountain

At the beginning of each player's upkeep, that player puts a flood counter on target non-Island land he or she controls. That land is an Island as long as it has a flood counter on it.
At end of turn, if all lands in play are Islands, remove all flood counters from them.

At the beginning of each player's upkeep, that player puts a flood counter on target non-Island land they control of their choice. That land is an Island for as long as it has a flood counter on it.
At the beginning of each end step, if all lands on the battlefield are Islands, remove all flood counters from them.