Bureau of Excursions

Bureau of Excursions enters the battlefield
tapped unless you control a mountain.
{t}: Add {r}.
{t}, Sacrifice a creature: Exile the top four cards
of your library. Until the end of your next turn,
you may play land cards exiled this way.
"Every year we send dozens of expeditionary teams
to the surface of Thag, and every year [REDACTED]
percent of them return!"