Borderlands: Mister Torgue's Arena of Badassery – Invincible Arena

Invincible Arena is a Standalone expansion that features an exciting new way to play the game – RAID BOSSES. Each Raid Boss is a battle unto itself, with unique modes of attack and shifting tactics that guarantee that no two fights are ever the same. Every battle is unique, with shifting boss modes and tactics. Four new Raid Bosses are introduced, as well as 4 new Vault Hunters. It's time to fight or Die in the Invisible Arena! —description from the publisher