Urza's Ruinous Blast
Legendary Sorcery
(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Exile all nonland permanents that aren't legendary.
Urza poured his love, his grief, and his hatred into the Sylex, and the Multiverse shook.
Illustrated by
The Brothers' War Commander#79RareEnglishLegality
Rulings
You can’t cast a legendary sorcery unless you control a legendary creature or a legendary planeswalker. Once you begin to cast a legendary sorcery, losing control of your legendary creatures and planeswalkers won’t affect that spell.
Other than the casting restriction, the legendary supertype on a sorcery carries no additional rules. You may cast any number of legendary sorceries in a turn, and your deck may contain any number of legendary cards (but no more than four of any with the same name).