If you control two or more other lands, Cave of the Frost Dragon enters the battlefield tapped. {T}: Add {W}. {4}{W}: Cave of the Frost Dragon becomes a 3/4 white Dragon creature with flying until end of turn. It's still a land.

If you control two or more other lands, Den of the Bugbear enters the battlefield tapped. {T}: Add {R}. {3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

If you control two or more other lands, Hall of Storm Giants enters the battlefield tapped. {T}: Add {U}. {5}{U}: Until end of turn, Hall of Storm Giants becomes a 7/7 blue Giant creature with ward {3}. It's still a land. (Whenever it becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)

If you control two or more other lands, Hive of the Eye Tyrant enters the battlefield tapped. {T}: Add {B}. {3}{B}: Until end of turn, Hive of the Eye Tyrant becomes a 3/3 black Beholder creature with menace and "Whenever this creature attacks, exile target card from defending player's graveyard." It's still a land.