Aberrant Manawurm (SOS 138)

Creature — Wurm • Mana cost: {3}{G} • Secrets of Strixhaven • Uncommon

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.

"What is the equation for terror?"
—Lost research note, Paradox Gardens

Illustrated by Lars Grant-West.