The Eternal Championship on Zakuul is found within the arena basement of the Platform 6 Cantina. Many of the Championships pitfighters can be found hanging out within the Cantina to all players that swing by, including the dynamic Duo known as Nocturno and Drake Raven, or as you probably know them: Batman and Robin.

Not only can you find them hanging out in the Cantina, but you can fight them in Round 7 of the Eternal Championship!
Drake Raven (Robin) constantly uses his utility belt to throw down Stun Grenades which can be used to keep Nocturno (Batman) away. Nocturno chases after you, and will hit with massive melee damage if they catch up.
While you fight them both, droids named G0-0Ns or Goons will spawn and kidnap companions and players.
When Drake Raven is defeated, you have the ability to loot his utility belt that comes with an assortment of tools such as stun grenades, a grappling hook, a button that summons Goons to fight and Shark Repellant.