Arcbound Tracker is a common Artifact Creature — Dog card from Modern Horizons 2 (MH2), collector number 112. Current market price: $0.24 (foil $0.32), TCGplayer market prices via Scryfall.
Menace Modular 2 (This creature enters with two +1/+1 counters on it. When it dies, you may put its +1/+1 counters on target artifact creature.) Whenever you cast a spell other than your first spell each turn, put a +1/+1 counter on this creature.