Gatewatch Beacon is a rare Artifact card from Commander Masters (CMM), collector number 721. Current market price: $0.34, TCGplayer market prices via Scryfall.
This artifact enters with three loyalty counters on it. {T}: Add {W}. Whenever a planeswalker you control enters, if this artifact has loyalty counters on it, you may move a loyalty counter from this artifact onto that planeswalker.