Aberrant Manawurm is a uncommon Creature — Wurm card from Secrets of Strixhaven (SOS), collector number 138. Current market price: $0.16 (foil $0.18), TCGplayer market prices via Scryfall.
Trample Whenever you cast an instant or sorcery spell, this creature gets +X/+0 until end of turn, where X is the amount of mana spent to cast that spell.