While the exact location of Pandemonium is itself subject to more than a few theoretical debates (with multiple correct and contradictory answers) one thing has been established. It is a rift into the realm of primal chaos and magic, where the rules change at the whim of powerful beings, up can mean down when gravity decides it is bored, animals speak fluently, trees spontaneously burst into piles of bubbles, you name it. It's madness personified, and all who enter risk their sanity as well as their lives. The fae and their cohorts abound in this place in a manner, able to carve out their own personal niche amongst the anarchy that otherwise rules. Magic becomes wild, blades turn to rubber, and one of the most dangerous things of all is a contagious and potentially life threatening case of the giggles, which can turn into full blown laughing fits for the weak willed.
The specific appearance of Pandemonium changes almost hourly, however some constants do seem to exist (either by will of its inhabitants or perhaps some greater rule which governs despite the madness). Giant mushroom as houses seem to be fairly common, as do towering trees with odd looking habitats, made with everything from sand to sandwiches, bolted on in fairly random places. The colours painted, splashed and thrown around are garish to behold, and occasionally fit inducing. The landscape shifts under the feet of travellers, and catchy jingling music seems to somehow fill the air, compelling the listener to start to whistle, hum and tap away to it, which in itself would not be a huge problem, except that each person hears a different tune.
For all its dangers however, Pandemonium represents one thing and that is pure magic of a scale and quantity known nowhere else. For this reason, many mages and those seeking their favour risk mind, life and limb to raid the lands of the Fae to steal this power. It's also rumored that all the riches of the fae eventually make their way into Pandemonium sooner or later, so stolen goods of immense value, as well as more than a few socks lost in the wash, can be recovered here. Those hunting items that simple cannot be found anywhere have occasionally stumbled onto them by accident here. The key seems to be to not look for them.
Sublocation of Primordia.