Sewer Crocodile

{3}{u}: Sewer Crocodile can't be blocked this turn.
This ability costs {3} less to activate if there are five
or more mana values among cards in your
graveyard.
"What can I tell ya? Bein' a reptile man ain't pretty.
But it's got its upsides. Like having the strength of a crocodile, for instance.
But I guess you've learned that by now, huh?"
—Killer Croc