Terrorpene is an ultra cool looking level 81 rare turtle. He shares the same model at Nemesis the elite quest npc which you more than likely have encountered if you've done any questing through Mount Myjal. Terrorpene can be found moseying along in the molten lava east of the Sulfuron Spire. (I have highlighted his patrol area in green on the map below.)
Terrorpene was meant to be a hunter pet. All he drops is a Crystalline Tear of Loyalty. If you see him up please ask a hunter friend to come tame him or announce that he is up in general chat, but please don't kill him.
You do not need to be BM spec to tame him, and he can be tamed at level 81. He is also immune to all traps. As you can see in the video below he hit me very hard during the tame. When you try to tame him he will use an ability called Burning Hatred that will tick for 10000 every second unless you have some sort of fire resistance. (Fire resistance gains quadruple effectiveness against this attack.) I had no resistances and it hit me for the full 10000 a tick. Being level 85 I had plenty of hit points to work with so I was fine, but lower level characters will need to take some extra precautions.
Using a Prismatic Elixir (increases magic resistance by 90), Elixir of Mighty Speed/Potion of Speed and any food buffs that give haste will definitely help to make this tame successful. Also, if you happen to have a paladin friend that can come along and give you their fire resistance aura that would also help tremendously.
Hunters that are specced BM can also benefit from using their core hound's Ancient Hysteria before the taming to greatly shorten the channeling time of tame beast.
As far as his spawn timer is concerned. I've heard of him spawning anywhere from 8 hours since he was last tamed or killed all the way to about 20.