Hmm? When trying to resurrect C'Thun, Cho'gall was stopped by Med'an. In the process, Cho'gall is horribly disfigured with a striking resemblance to C'Thun (tons of eyes and thorns) and powers resembling C'Thun's.
C'Thun is clearly very close to if not a part of Cho'gall:
(The claws of fate grasp the unbelievers!!)
What madness have we wrought... (Not yet enough!)
I... can't take much more... (Brother, it merely begins!!)
(The Master sees, the Master SEES!)
(The Master's eye sees all that was and all to be, or not!)
Brother... we are shattered... (But The Master... I still hear... so angry... Master...)
Brother... we are shattered... let her... finish them... (The Master... does not want them near her... Brother... The Master seethes...)