It IS Xau-Tak, the sailor from the SECOND AGE mentions the character name far before they are even born. Xau-Tak knew that we could potentially be a problem. The diary it is set in is from when the asylum in Silvarea is active, this is very disturbing.
Also, i think that maybe the yellowish dialogue that we see is the 6th unborn elder god. It is a well known theory that the elder god is the one, 'not of form' and i believe Sliske knows this and serves it to gain his own power.
It won't be Nomad for me, I made sure that he was dead in Elegy.
I think it is the 6th Elder God, who some are speculating their name, Vos, who is inside the egg who needs to hatch. I think Jas failed to hard-boil the stone of jas correctly and now he/she is mad. Vos needs a vessel. Sliske will provide this vessel. The most powerful God, and guess the two most powerful gods. Seren and Zaros, they are both in the endgame.