User blog comment:PsijicThief/A New Guild/@comment-8248675-20131011235358/@comment-7153552-20131012195352

The Morag Tong did not begin as Empire Sanctioned, it was around before the Empire ever got into Vvardenfell. It is said to have been founded by Mephala, she taught the Chimer (before the Dunmer, before the Empire) how to evade enemies and destroy from within with secret plots. A small faction of the Chimer held onto those beliefs and principles ever after the emigration from Summerset Isles and formed he Morag Tong. It is known for being a legally sanctioned organization of assassins.

All of that is seen here.