Looks like the Sage will have to come down with the info. (Especially since Yugman isn't around, the poser.

)
[Editor's note: This contains spoilers for the short story: "Three Dreams of Belsameth", and the books: Forsaken and Forsworn]
Now that we have that out of the way....
Regarding Jandaveos,
As many of you are aware, the History of Termana and indeed the Scarred Lands tends to be subjective. I, however, being a student of history, will try to be as objective about such matters as possible.
To begin with, the death of Jandaveos, or as he was called after the Divine War erased all of traces of his name, That Which Abides, was caused by Chern's rage against the forsaken elves or as some places might call them "High elves" Because of the large scale devastation caused by plunge Kadum took into what is now called the Blood Sea, much of the Charduni army on Termana was destroyed and the Forsaken elves managed to rally their armies to prepare for a strike against their weakened foes. However when Chern came, and using a guile not relatively known to him, infiltrated the Herald of That Which Abides and killed him, much of the fall of those elves was readily apparent. However while the Curse of Chern was great, the death of their god was nearly a death blow. That was until one last high priest, one Vladwen Titanslayer, decided to go on a most perilous quest. To ressurrect his god. In that action, he also became ensnared in the designs of the Slayer herself, Belsameth. Seems the Lady of Murder, much like the rest of her kin, was feeling the need to shore up the divine ranks a little. Plus the fact she felt she needed a new patsy to play with. So with the aid of the Prince of Shadow himself, Dar'Tan, the Penubral Pentagon's leader, she devised a scheme where by Vladwen would not only ressurect his god, but alter him enough to gain his alliegence to the forces of "evil." So after giving Vladwen "gifts" and plots more myriad than most mortals care to comprehend, she and Vladwen succeeded in raising the god. (The start of which was a small religious war in Darakenee that also raised belief enough to give That Which Abides the power to at least be able to break free). The means of which was secured by the High Council of Hollowfaust's own, along with an artifact of Slacerian design (one of their muses that had yet to be enspelled and thus unaffected by the demise of That Which Abides). So when the true ritual was cast, Jandaveos returned. However Vladwen, with the aid of Kadum, the Thunderous One, thwarted both Belsameth's and Dar'Tan's scheme. While the exact details of the barter between the two entities is unknown to me, I believe Kadum himself used his blood to break the hold that Belsameth had over Jandaveos and thus secure his "goodness" to all.
Now it seems that the Dark Elves might try something similiar, though of course this is speculation on the part of this historian and sage. Still it is worth considering such things.