Deekah, Fractal Theorist (Extended Art) (C21-353) [Commander 2021]

Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is that spell's mana value.
{3}: Target creature token can't be blocked this turn.