Tunnel Tipster is a common Creature — Mole Scout card from Murders at Karlov Manor (MKM), collector number 180. Current market price: $0.18 (foil $0.19), TCGplayer market prices via Scryfall.
At the beginning of your end step, if a face-down creature entered the battlefield under your control this turn, put a +1/+1 counter on this creature. {T}: Add {G}.