Heroic: Ra-den

Just a hunch but Ra-den's blood could be used to empower mogu flesh shaping experiments.

If you look in the dark animus' dungeon journal (http://www.wowpedia.org/Dark_Animus#Dungeon_Journal)
It says: "To this day, the ornate construct observes its duty, empowered by the mysterious substance at the heart of all mogu flesh-shaping experiments."

Looking at this photo of the dark animus you can see a blood like substance in it's core http://img.mmohelper.ru/a/a/5-2-frame/9-dark-animus.jpg

It is the gouges in ra-den's limbs that gve me this idea as shown in this photo posted by Reignac http://media.mmo-champion.com/images/news/2013/january/TitanCaptured.jpg

Perhaps Ra-den is being held captive or he made some sort of deal with lei'shen, Ra-den's dungeon journal says "No one knows what transpired between the two beings".Looks like we will have to wait for 5.2 to hit live before we find out though!

The title says "Heroic", but the text of the achievement doesn't mention that. Maybe he will be the extra boss on heroic difficulty...

Ra-den is a Titanic Watcher. Like Thorim, Freya, etc. in Ulduar. Model:
http://media.mmo-champion.com/images/news/2013/january/TitanCaptured.jpg

Dungeon Journal says:
Lei Shen's life changed forever when he stumbled into a dark chamber below what are now the Mogu'shan Vaults. Legend has it he found an ancient titan keeper guarding a miraculous device known as the Engine of Nalak'sha. No one knows what transpired between the two beings, but Lei Shen later emerged from the site bristling with the power to forge an empire. The keeper's fate -- and his current whereabouts -- remain a mystery.