The Ancient Egg: an ancient artifact holding the essence of spirits captured. Had Elortha no Shadra-spirits in it for a long time, and the Kaiju Spider, venerated religiously in Jintha'alor.
The Egg was in Jintha'alor, but a Ravenholdter team shook it loose during the confusion of Jin'tek's overtaking of the city. The high priestess summoned the Kaiju spirit to fight Lethon, but the spell was stopped and the spirit returned. However, the Other snatched it from the agents and took it to Alterac to grow strong off its energies. The pagans - Meryl, specifically, under the name BJ, possibly via Ba'jal - orchestrated the events to suck in the essence of Alterac's dead gods into it.
Very little of Akaerna-Sagai made it into the egg as her essence was largely contained in Hellen von Xie, who died before her essence could be transferred - in an explosion that took out the other physical Xie-vessels of Akaerna-Sagai's blood. But Caxagord defeated Xie and sucked Xie-Other- Xostheron into it. Meryl then got the Egg and absconded... somewhere?Somehow it turned up in the hands of the Council of Tirisfal/Ravenholdt; I don't remember how.
Lethon accompanied the Companions to Venege. At Venege's dust-up, Lethon took the Egg from the Council of Tirisfal. He said the Greens are fighting their own war, and implies the Egg have dragged the poor mortals into it.
Lethon returned the Egg to Jintha'alor, it being integral part of their religion and spider-goddess. He demanded they leave it out of the War. They hoped Shadra would be reborn from it, pure as their faith was pure.
But, Arronax' agent-shades stole the Egg. Snap, baby..