Located in the treacherous Wilderness, the Chaos Elemental is a bizarre creature that can drastically put a damper on your experience through its erratic attacks and behavior. Fellow players may also come to put an end to your boss slaying, so take care!
For the quickest way to get to the Elemental, teleport to Edgevile and go into the ruins south of the bank. Find the lever and pull it to enter the Deep Wilderness (level 50+!!). Exit the Deserted Keep and run east and scout the area to find the Elemental.
LP: 17,500 LP
Attack Styles: All
Max hit: 1000
Note that it can hit with Melee even far away, so be a bit more careful if Ranged with fairly weak armor!
With the Elemental comes two special attacks. One is when you will be randomly teleported away to a random location away from the Elemental (signified by a red blast), and the other one (signified by a multi-colored attack) unequips your mainhand weapon and up to three armor pieces equipped. The latter can be avoided by having a full inventory.
Hit it until it dies, and keep a full inventory as much as possible. As such, brew vials (with vial-destroy function turned off), summer pies, and other such food are great for the Elemental if you need supplies. Use Protect from Magic or Soul Split as your default prayer.