Hlaungadath portal

The Hlaungadath portal was a magical passageway located within the temple of Mystryl in the Netherese city of Hlaungadath.

Description
The portal was 7' (2.1 m) high and 6' (1.8 m) wide, shimmering with blue light that was bordered by a glow that quite resembled faerie fire. It was believed the lines of the dwarven song that activated the portal were inscribed nearby to its location, though any proof of this was lost amid the ruins of the city.

Activation
While the known function of the portal was as a two-way passageway to the dwarven city of Ascore, it had a number of secret destinations that were known by its creator. The portal was activated by the recital of a thirty-line dwarvish chant, short for their kind, which ended with the line (roughly translated): ""...that the halls of our fathers may stand for 10,000 years""

By altering the number of years in the last line, the destination of the portal could be changed. If they changed the chanted lyrics to "for 1,000 years" the portal opened up to the Astral Plane rather than Ascore. The key was as follows:
 * "1,000" – Astral Plane
 * "2,000" – Miyeritar
 * "6,000" – Anauria
 * "12,000" – Myth Drannor

History
Created during the glory days of Hlaungadath, the portal allowed for ease of travel between the Empire of Netheril and the dwarven realm of Delzoun. While the creator of the portal could use it to access other locations, they were extremely forgetful and wrote the alternate lines in a journal, but it had been torn asunder and scattered across the ruins of the city following the Fall of Netheril.

Centuries after the empire fell, the portal continued to operate, but several of its alternate pathways no longer transported to their exact intended destinations. The passageway to "Myth Drannor" opened up into the hollowed interior of a great tree some three miles north of the city, the opening to "Anauria" led to the city's ruins deep under the sands of the Anauroch desert, and the path to "Miyeritar" led the traveler to the center of the High Moor.

In the 14 century DR, a group of lamias, led by the noble Koreeis, were fleeing from some Bedine raiders when they stumbled upon the ruins of Hlaungadath and discovered the portal. They weren't immediately able to activate the magic passageway, but rather began scouring the desert for some spellbook or sorcerer who could reveal its secrets.