Originally used for a quest that was part of the quest chain for the Dungeon 2 set. It can no longer be acquired due to the removal of all the Old Azeroth dungeon set quests. However, players who did the quest prior to its removal and didn't destroy it afterwards are still able to use it to challenge Theldren and his cronies. This is the only means of "summoning" Arena Spoils.
Arena Spoils has the following loot table:
I am very happy that I held onto mine. I almost didn't because it was yet another slot being occupied in a very finite inventory, but fortunately events went like this: "You know what? I'll just keep it and delete something else."
Sadly, this was not the case with my Brazier of Invocation. (ಥ﹏ಥ) Prior to Cataclysm, I could always revisit the NPC and acquire a new one - which likely figured into my reason for destroying the brazier in the first place.