Belbe, Corrupted Observer is a rare Legendary Creature — Phyrexian Zombie Elf card from Commander Legends (CMR), collector number 270. Current market price: $0.37 (foil $0.64), TCGplayer market prices via Scryfall.
At the beginning of each postcombat main phase, the active player adds {C}{C} for each of your opponents who lost life this turn. (Damage causes loss of life.)