Arsenal Thresher is a common Artifact Creature — Construct card from Alara Reborn (ARB), collector number 131. Current market price: $0.11 (foil $0.20), TCGplayer market prices via Scryfall.
As this creature enters, you may reveal any number of other artifact cards from your hand. This creature enters with a +1/+1 counter on it for each card revealed this way.