Alhammarret, High Arbiter (ORI 43)

Legendary Creature — Sphinx • Mana cost: {5}{U}{U} • Magic Origins • Rare

Flying
As Alhammarret enters, each opponent reveals their hand. You choose the name of a nonland card revealed this way.
Your opponents can't cast spells with the chosen name (as long as this creature is on the battlefield).

Illustrated by Richard Wright.