Sea City

Landfall-Whenever another land enters the battlefield under your control,
target player may mill ten cards. if that player
does, they get an extra turn after this one
{t}: Add {u}
Whenever a triggered ability causes a player to
take an extra turn after this turn, you become
fortified on that turn. (You cannot be attacked
by creature's the player whose turn it is controls
until the end of turn.