Board Thread:Warhammer 40k General Discussion/@comment-14745711-20140928092626/@comment-25451195-20140929111407

well you see, The Emperor was still "around" for a while, and was still providing... highly limited direction on events. (Unless recent Canon states that on internment of the golden thrown he went utterly silent) but even then it was not instant like, the survivng loyalist primarchs became the war leaders and administrators in absentia.

however, in the most extream notion, people above have stated what i also think would be true, a Primarch seeing the difference of 10,000 years would toss his cookies in rage and disgust over the horrible mismanagement of His fathers domain. also depending on which on it is... if RG came back, he would crack his nuckles, neck and back and then near bloodlessly IMO ascend terra to be the new Emperor... RG was an administrator who was only equaled by The Sig and The Emperor.