Grolnok, the Omnivore 
Legendary Creature — Frog
Whenever a Frog you control attacks, mill three cards. Whenever a permanent card is put into your graveyard from your library, exile it with a croak counter on it. You may play lands and cast spells from among cards you own in exile with croak counters on them.
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL