Arcane Chimaerok

An Arcane Chimaerok was one of three types of chimaeras previously inhabiting the Isle of Dread off the coast of Feralas. They dropped Chimaerok Tenderloins which were needed for Quest:Dirge's Kickin' Chimaerok Chops, which was a part of Scepter of the Shifting Sands questline from the Gates of Ahn'Qiraj opening.

Tactics
Arcane Chimaeroks had the ability to reflect magical attacks during combat, similar to a paladin bubble. One had to be careful as it was easy to you can crit yourself with a spell while this ability is active.

Notable drops

 * Chimaerok Tenderloin

You could get this from all types of chimaera on the isle. It was not a 100% drop, perhaps about 67% chance to get it from each kill. You may have needed to kill all the Chimaeroks 3 or 4 times to get 20 Tenderloin. The chimaeras took some time to respawn.

Cataclysm
As the Isle of Dread was destroyed in the Shattering, it seems all the chimaeras, including the "Arcane Chimaeroks", perished. Neither them, nor another source of delicious Chimaerok Tenderloins, have been found since.