Magmablood Archaic is a rare Creature — Avatar card from Secrets of Strixhaven Promos (PSOS), collector number 123p. Current market price: $0.34 (foil $0.64), TCGplayer market prices via Scryfall.
Reach, trample Converge — This creature enters with a +1/+1 counter on it for each color of mana spent to cast it. Whenever you cast an instant or sorcery spell, creatures you control get +1/+0 until end of turn for each color of mana spent to cast that spell.