600 years ago, a group of elven researchers from Silverymoon led by head-research Erdanis, travelled to Desert to establish an observatory to observe the planar influences in and possible motives for its rejection of Divinity. Eventually, their research progressed enough that Erdanis was able to utilize the observatory to see into the past and consequently finding out the origin of Desert.
On the day of the experiment, it is unknown what Erdanis saw, but he turned mad. He locked himself into his quarters and envisioned terrible aberrations from the stars. Eventually he died of starvation but his spirit turned into an aberration made of worms, which he used to massacre the other researchers and also turn them into aberrations.
Centuries later, a team of mercenaries led by the Half-Elf Valathuriel was sent by Doctor Craven to investigate the mystery behind the tower. The team was massacred and Erdanis revealed the truth that he saw to Valathuriel, which turned her as mad as him.
In 1486 DR, the Seekers were sent on a follow-up investigation by Doctor Craven. They faced and defeated the many horrors of the tower and finally faced Erdanis and a maddened Valathuriel. Upon their defeat, Valathuriel whispered of the Divine Worm, turning herself into a cosmic aberration, which fought against the party, assisted by an Erdanis-possessed Connor Lycanmor. The Ascended Valathuriel met her end at Ellora Oak and her body disintegrated due to not being capable of handling the power she was given.
Connor Lycanmor was eventually purified of the possession, but at the terrible cost of Ulgyr becoming comatose.