Chamber Sentry is a rare Artifact Creature — Construct card from Guilds of Ravnica (GRN), collector number 232. Current market price: $0.24 (foil $0.39), TCGplayer market prices via Scryfall.
This creature enters with a +1/+1 counter on it for each color of mana spent to cast it. {X}, {T}, Remove X +1/+1 counters from this creature: It deals X damage to any target. {W}{U}{B}{R}{G}: Return this card from your graveyard to your hand.