Enigma of Sotha Sil

 appears during the quest The Seal of Three located in the Tribunal Temple. According to it, it is the essence of Sotha Sil's imperfections cast away by Sotha Sil himself.

Quotes

 * "We are the imperfection of Sotha Sil- excised from his being, yet never truly apart. We measure the indulgence of inspiration against the necessities of progression. You will never know. You are not Sotha Sil."