Watcher of the Spheres is a uncommon Creature — Bird Wizard card from Core Set 2021 (M21), collector number 227. Current market price: $0.63 (foil $6.65), TCGplayer market prices via Scryfall.
Flying Creature spells with flying you cast cost {1} less to cast. Whenever another creature you control with flying enters, this creature gets +1/+1 until end of turn.