Balor's Gaze

(You may cast a legendary instant only if you control
a legendary creature or planeswalker.)

Exile target creature or planeswalker. Each player
loses 3 life.
"Balor, Champion of the Fomori, opened his single
eye, and his Gaze unleashed the powers of death and
poison unto the world."
Excerpt from the Cath Maige Tuired