Landfall — Whenever a land enters the battlefield under your control, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)
A landfall ability doesn’t trigger if a permanent already on the battlefield becomes a land.
A landfall ability triggers whenever a land enters the battlefield under your control for any reason. It triggers whenever you play a land, as well as whenever a spell or ability puts a land onto the battlefield under your control.
Whenever a land enters the battlefield under your control, each landfall ability of the permanents you control will trigger. You can put them on the stack in any order. The last ability you put on the stack will be the first one to resolve.