Fourth of Six Paths
Deva Path (Presumed)
Not much is known about Shiens past, other than that he hails from the almost extinct Uchiha clan and was an accomplice of Tobi. However, it has been revealed that he was Tobis personal medical assistent during the Fourth Shinobi World War. After the war, he was hunted down by Konohagakures ANBU black ops and was thought to have been killed.
Five years after the war, he reemerged as the leader of the reborn Akatsuki. He personally recruited Genzo Netsuishi to his group and was shown to have obtained the Rinnegan through unknown means. He has yet to show his true face, since he mainly acts through his Six Paths of Death.
Being the leader of the Akatsuki, Shien constantly displays an emotionless personality. While acting through his Deva Path of Death, his face is covered by his mask so that no facial expressions is shown. However, he seems to have more personality than Tobi as he doesn't hide who he really is and has no problem speaking out of personal thoughts.
Also, he seems to have quite different views from his former partner, as he stated "Tobi was an idealist, I am a realist".
AppearenceEditThe only part of Shiens true appearence to have been shown is his sillhouette, which bears a small resemblense to Madara Uchiha. He normally acts through his Deva Path, which was created from Tobis corpse. He has, however, reverted to the dress Tobi originally wore, with an Akatsuki cloak and the orange, swirl-patterned mask which only shows his right eye. Another notable difference is that the right eye shown contains a Rinnegan instead of a Sharingan. Since the paths shares the same eyes as the user, it can be assumed that Shiens true body also has the Rinnegan in his right eye. It is unknown if both eyes are Rinnegan.
Not much is known of Shiens true abilities. However, it can be assumed he is very powerful as he can control an organisation as powerful as the Akatsuki. Also, as a bearer of the Rinnegan, he can potentially master all six Nature Transformations.
Six Paths of DeathEdit
The only known technique used by Shien so far is the Six Paths of Death. This is simply a renamed Six Paths of Pain, having the same capabilities and drawbacks. The only one shown so far is the Deva Path, which was created from the corpse of Tobi. Since Shien names the paths, it can be assumed that they are at least given the ability of the name, like Nagatos paths. It is yet unknown if they keep their bodies original abilities like Tobis did.
(To Genzo) "Every shinobi have a strong point and a weak point. If you find their weak point, every shinobi can be defeated."