Grenzo, Dungeon Warden is a rare Legendary Creature — Goblin Rogue card from Masters 25 (A25), collector number 205. Current market price: $0.50 (foil $2.83), TCGplayer market prices via Scryfall.
Grenzo enters with X +1/+1 counters on it. {2}: Put the bottom card of your library into your graveyard. If it's a creature card with power less than or equal to Grenzo's power, put it onto the battlefield.