Board Thread:Theories and Speculation/@comment-1512913-20150221101637/@comment-6769189-20150222095356

Ok, things get weird with Susanoo. It is the only ability this far that isn't focused on actual vision. Itachi has activated it without MS, but lost it when he went blind. Sasuke also lost it once his eyesight faded. Madara activated it WITH NO EYES AT ALL!
 * So it is possible the EMS grants the ability use Susanoo no matter what, as vision isn't necessary to use it. It seems this technique is not held in either eye. Obito never used his because he was in an super weak state when he got both his MS.
 * So it would seem switching between EMS and Rinnegan is necessary. HOWEVER, the Rinnegan can basically create jutsu and allow mastery of Yin, Yand, and Yin-Yang, so he should have been able to do MS stuff anyways. Maybe switching was just easier.
 * The Rinne Sharingan would basically be Sharingan through Rinnegan all at the same time. The Sharinnegan is a weaker variant of this.

Tensigan doesn't seem to be related to the Rinnegan at all in terms of formation. It would seem the Tenseigan: 1) Didn't happen with Kaguya because the Rinne Sharingan was stronger, so natural selection. 2) Was dormant in Kaguya because she didn't push the Byakugan because the Rinne Sharingan got the job done 3) DID happen with Kaguya, but wasn't used because the Rinne Sharingan got the job done