Kozilek's Sentinel is a common Creature — Eldrazi Drone card from Battle for Zendikar (BFZ), collector number 129. Current market price: $0.15 (foil $0.20), TCGplayer market prices via Scryfall.
Devoid (This card has no color.) Whenever you cast a colorless spell, this creature gets +1/+0 until end of turn.