The Battle of Dragon Brothers // Fate Reforged (Unknown Event RC07b) - Rare Magic: The Gathering Card

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When The Battle of Dragon Brothers Enters, choose Bolas or Ugin.
• Bolas — Destroy all creatures.
• Ugin — Manifest the top three cards of your library.