The Djinni's second task. You start by going through a standard blue portal to this new map. There's a local jump portal, and then you have to follow the luminous circle, and stay inside it. It leads to substantial danger. Outside the circle you will take non-stop damage, multiple times per second.
First Play Through
On your first trip through the game, if your health regen is high enough, and you can caste the occasional healing spell, you can ignore the circle of safety, and keep away from the opponents, so as to not take them all on at the same time. It helps to run the Salt Barrens entire map two or three times so as to be several levels above the spawning opponents.
Secound Play Through
At higher level (second game run-through, above level 50), you will really need your armor pumped up, because you won't be able to have a high enough health regen (120 is achievable, and is nowhere near enough). So you have to stay in the circle.
That means you are in another cage-fighting episode. You will want to be able to summon plenty of helpers (skels and archers and whatever else), swill potions like they are going out of style, shoot like mad, and run in circles a lot. Each time the illuminated circle stops there is a crowd to fight, with at least one "boss" character. There is a good chance you will get swarmed and killed. The circle will stop several times like this. You do not really get a chance to pause. If you armor up pretty far, have good regen, cast spells, swill potions, summon like mad, you won't have to spend too much time in the circle.
There is no way to restart this map partway through--every single time you begin at the beginning and have to re-fight all the same little battles.
At the end of the first section of the Arena, when the circle pauses by an orange teleport pad and a giant chest. A secret lever will appear if you want for several seconds by the pad. The lever activates additional platforms that will take you to a room to the north. In that room are two giant chests and a mysterious shadow that will have an Eye of Gallo.