I couldn't help but notice, however, that it's hard to reconcile this timeline of Unther with the novel The Alabaster Staff, set mostly in Messemprar.
To take a fairly major problem, Gilgeam-ite lords have very different fates. Lords Ekur and Zimrilim were alive and well at the beginning of the year DR 1373 and the novel makes clear they went into hiding immediately upon the death of Gilgeam in DR 1358. They've been in Messemprar for at least a decade, probably the full 15 years.
I gave a lot more love for the old empires than this scroll (which was a beginning). If you check out the alternate dimensions links in my sig I devoted issues 3, 4, 5, and 6 I think to expanding unther, mulhorand, and thay. I even tried writing up a brief campaign centred around the conquest of unther.
I'll admit none of this (or anything I do) is compatible with novels. The novels are a resource I do not possess and so I concentrated on what was in the sourcebooks instead. I'm not sure how many people have read the novels but you are the first to mention ekurs fate in them. I view the novels as someone else's story/version of events. In the end I made a nod to the alabaster staff and zimrilim was involved in giving unlife to gilgeams avatar. These aspects of Gilgeam were then involved in a highlander style conflict that saw Gilgeam return as the untheric god of madness and undeath. This however was just part of a greater storyline involving the conquest of unther and merging of the mulhorandi and untheric pantheons.
I hope to revisit the old empires again, they were a lot of fun