Trader Sarien:
A letter from Priestess Vivyan? The grave of Paladin Kelhas and Commander Kiruna? Well... Surely there were many graves of the Elmoreden era here... But sandwind was vicious, and what's even more, the giant ants excavated the place... I bet that all the graves and the relics in it have disappeared by now.
Although chances are scarce... I would try the ants tunnel if I were you. According to the adventurers who investigate the Wastelands, they say that the ancient relics are found in the ant tunnel now and then. Perhaps the remains that you are looking for might have been excavated by the ants as well.
If my guesses aren't wrong, it must be the soldier ants who carry such things as bones and remains. They normally cut things into pieces, such as a human corpse. Well... Perhaps 5 pieces...? I'll give you this illustrated book for reference. It will help you when you are exploring the ant tunnel. Good luck, then!