The Librarian

When the Librarian enters the battlefield, gain
{x} where {x} is the number of different
creature types on the battlefield.
{u/b}{u/b}{t} Target Player puts the top of their
library into their graveyard.
If it's a creature you gain {u/b}{u/b}. If that creature
does not share a creature type with a
creature on the battlefield gain {u/b}{u/b}{u/b}
or you may play that creature until end of turn.