Sumala Sentry is a uncommon Creature — Elf Archer card from Murders at Karlov Manor (MKM), collector number 233. Current market price: $0.14 (foil $0.09), TCGplayer market prices via Scryfall.
Reach Whenever a face-down permanent you control is turned face up, put a +1/+1 counter on it and a +1/+1 counter on this creature.