Zhentil Keep

Zhentil Keep (pronounced: /zˈhɛntɪl kip/ z-HENT-ill keep), also called Thargate Keep, was once the most powerful city in the Moonsea region as well as the main base of operation for the ZHENTARIM . Along with the Citadel of the Raven, Zhentil Keep was destroyed by the Shadovar in 1383 DR after it was discovered that the Zhentarim had forged an alliance with the phaerimm.

https://forgottenrealms.fandom.com/wiki/Zhentil_Keep