Editing Sky Serpents (section)

==>Tlaloc Tzotz, Lord of the Count, the Blind Seer, the Exile==
During the crusade and the heresy, Tlaloc was a member of Xun's inner circle. A librarian of rare power, even in a legion known for its command of warp craft, Tlaloc testified at Nikea and went on to play an important role in many of the battles of the Solar Rim campaign. However, on Prospero, Tlaloc seems to have come under a strange influence.
Whether a tome, a phantasm of the warp, or something else, Tlaloc began to diverge from the cautious Path of Heaven of Xun and Tepectitlan.
In the aftermath of the Heresy, Tlaloc initiated unorthodox experiments in the Warp, looking for better ways to fight the neverborn. Specifically, Tlaloc developed a ritual similar to the soul binding performed by the Emperor on Astropaths. While this protected librarians from the neverborn and increased their ability to slay them, it delved into strange xenos lore of the dancing eldar.
Xun was furious that Tlaloc had done this without approval, even as Xun developed his own method for soulbinding.
For this breach of trust, Tlaloc was cast out from the Legion, with nothing but a small band of retainers.
From then on, though allowed to meet with members of the Legion, Tlaloc was on his own. Xun being Xun, a path to redemption was left open. If Tlaloc could gather all the data, then he would be allowed back.
Still devoted to the cause of the Imperium, Tlaloc seeks for a way into the legendary Black Library of the Harlequins.
In this task, there is none he will not work with and nothing he will not do. He has raided Angelic Abbeys and Asuran Libraries alike.

(I'm thinking he still has his library card to the Sky Serpents. Xun basically couldn't condone his reckless acts, but seeing how the censure of Oramar turned out, he figured he'd try something different with his own son. The results are mixed.)