Berta, Wise Extrapolator (SOS 346)

Legendary Creature — Frog Druid • Mana cost: {2}{G}{U} • Secrets of Strixhaven • Rare

Increment (Whenever you cast a spell, if the amount of mana you spent is greater than this creature's power or toughness, put a +1/+1 counter on this creature.)
Whenever one or more +1/+1 counters are put on Berta, add one mana of any color.
{X}, {T}: Create a 0/0 green and blue Fractal creature token and put X +1/+1 counters on it.

Illustrated by Tuan Duong Chu.