As lore goes... The kerrans, and the heratics of Erudin Fought over control over odus. The heretics, in an attempt to end the fight between them, unloaded a massive, powerful magical attack, that blew a large portion of odus off the face of the map. The large chunk of debris flew up into the air, out of the atmosphere of norrath and collided with luclin.
The remains from that impact, formed some of the initial ruins on the face of luclin, forming areas like Madiens eye, and Akehva. The Kerrans who were left alive on this chunk of debris, crawled off upon landing, and wandering, eventually founding the city of Shar val.
Back on Odus, The consequential damage breached into the plane of the underfoot, which the heratics of Erudin claimed as their own, and Founded the city known now as Old Paineel. The heratics however were overwhelmed by the monsters that creeped out of the tunnel systems as the heratics pushed deeper and deeper into what was the plane of underfoot. Eventually, the heratics finally decided to abandon it, climb back out of the hole, and found the current city of paineel.
MMMM history lesson.