Karsoluthiyl Karsoluthiyl was a drow city located beneath the Trackless Sea , west of the mouth of the River Chionthar . Two prominant houses were House Tanor ' Thal and House Lysaen . Both houses were big players in the slave trade of Skullport . Geography . Karsoluthiyl is located in a region of the Underdark known as the Swordsea Depths , which lies underneath the Sword Coast . They are engaged in a struggle for supremacy with Aboleths , Svirfneblin , and Thaalud who also call the area home . It is connected by long and arduous tunnel routes to Undermountain to the north , Sshamath to the east , and the realms of Deep Shanatar to the south . In addition it is at the end of a series of portals which link from Karsoluthiyl to sea caves in Ruathym , from there to caverns in the Crags near Neverwinter , to the Undermountain , another set of caves in Ruathym , and back to Karsoluthiyl . History . Although some claim that Karsoluthiyl was founded by House Tanor ' Thal in - 105 DR , the Year of the Bloody Goad , Drow from the city were identified as being at war with Clan Melairkyn as early as - 677 DR ( Year of Fervent Glances ) . The war was sporadic until the Drow attacked in force in 34 DR , bypassing the dwarven defenses through magical disguise , levitating up Belkram ' s Shaft , and killing Melair IV , the last king of Melairbode . They proceeded to re - purpose the dwarven halls to their own needs , building up the outpost of Kyorlamshin , and even building a barracks and martial academy , the Citadel , and the Crystal Labyrinth . Their success was only to be short lived as Halaster ' s arrival in the Undermountain precipitated Halaster ' s Hunts which started in 171 DR and ended with the Drow withdrawing completely from the Undermountain by the Year of the Ecstatic Priest , 493 DR . During this time many Drow were also captured and twisted by Halaster ' s apprentice Muria l into " Murial ' s Creations " . A series of Drow raids occured along the Sword Coast and resulted in the destruction of the small kingdoms of Harpshield and Talmost . The Drow were unidentified , but given the location it seems reasonable to suspect Karsoluthiyl . Drow in the area also attempted to excavate the Netherese ruins of Philock . Philock lies in the tunnels between Karsoluthiyl and Sshamath . In 1163 DR the Jaezred Chaulssin returned from the Plane of Shadow to the Prime Material Plane and established a fosterage in Karsoluthiyl among other cities . This fosterage went under the guise of the wealthy merchant House Oussghym . At least two centuries later the house was led by Patron Father Quildan Oussghym , and had developed a rivalry with House Lysaen . Karsoluthiyl was one of the cities in which the Jaezred Chaulssin were able to weaken the power of the matriarchy during the Silence of Lolth . At some point the Drow re - established links with the Undermountain , being heavily involved in the slave trade in Skullport , as well as competing with Duergar to sell Deep Rothé meat and hides . House Tanor ' Thal dominated the trade from Karsoluthiyl due to their control over the portal system . Their interests there were great enough for Matron Mother Haelra Tanor ' Thal to send her niece Kesra to act as de facto Matron Mother in Skullport , and building a massive spider shaped compound . House Lysaen attempted to establish their own presence , under the guidance of Ahlysaaria Yril ' Lysaen but they were forced to travel a long physical route , part of which was above ground through the Forest of Wyrms , presumably to stop at the ruins of Tholhtzin where the Serpentfolk of Najara purchase slaves . Other threats included Malakath Tabuirr , head of the Dark Dagger who originally hailed from Karsoluthiyl . His house was destroyed by House Tanor ' Thal and he escaped , changing his name to Tabuirr . He used his position and organization to secretly undermine House Tanor ' Thal ' s commerce by attacking their caravans . During the Spellplague much of Skullport was destroyed , and described as being only home to houseless Drow , suggesting that much of the various Karsoluthiyl interests were no longer operating .