Dartain of the Dark Truth
An ancient Erudite Heretic who was sealed inside the Underfoot after placing the Hatch to repair the Wall of Living Stone, surviving there for centuries until inadvertently freed by Ognit's experiments.
Overview
Drawn from knohole9 — in-game book.EQ1Primary · official · best available source
Dagda wiped her eyes and brought herself up to her full height. She asked Al'Kabor, "Who is this Dartain?"
Al'Kabor answered, "Dartain is one of the heretics. A heretic of old. He was among those that put The Hatch in place to repair the Wall of Living Stone. Through his own misfortune, he managed to get sealed on the other side of the wall in the Underfoot, while his companions were slaughtered to a man. He was able to complete the ritual from the Underfoot side and The Hatch was put in place successfully. The Underfoot was sealed off from the rest of the world and the danger ended. Everyone assumed he was dead afterward, of course."
Dagda looked confused and stated, "He is certainly not dead. We saw him this day with our very eyes. Though he appeared pale and weak, I know that hot blood filled his veins. By what magic is he still alive after all this time?"
Al'Kabor looked up for a moment thoughtfully. He then hypothesized, "The Altered Planes are much different from our world here. It is indeed possible that by virtue of the elder magics that course throughout all of the Underfoot and the other Planes, that mortals age differently there."
Then he added, more to himself then to anyone else, "No doubt the Heretics will gain in strength with his release and I will not stand idly by while this happens. I must go and prepare. I can not allow Dartain to remain in this realm while I draw breath."
Al'Kabor stopped for a moment and stroking his chin reflectively said, "Perhaps some good will come of this. Maybe the denizens of the Underfoot will finally destroy the heretics in Paineel before The Living Wall is able to heal itself." He then walked away back through the city gates.
Dabner grabbed Dagda by the hand and cried, "Oh Dagda, what are we going to do? What about Ognit and Odus and Dartain and everything!"
Further sources
1Lore that mentions this in passing.