Repost: Geography Info
The Marketplace of Mantol-Derith is 2 to 3 days travel on foot from the secret portal you used to escape Menzoberanzan. This market was where the Drow of Menzoberanzan used to trade with the Svirfnebli of Blindenstone (before Menzoberanzan wiped out Blindenstone and sold the surviving Svirfnebli in the marketplace as slaves). There are usually Drow Merchants, Duergar merchants, and a variety of merchants from the surface world in Mantol-Derith.
Other nearby landmarks from Mantol-Derith: Within 3 to 9 days travel on foot: Menzoberanzan, the ruins of Blindenstone, the Gray Dwarves' city of Blades Gracklstugh, the Labyrinth, the DarkLake, and the merchant house of L'Tar'annen de’l Elgluth.
Other Drow Cities: Ched Nasad, Maermidrya, and Sschindylryn are all 12 to 25 days away on foot.
Commonly known info on nearby landmarks and communities:
http://www.wizards.com/default.asp?x=books/fr/underdark
Map of the Underdark
http://www.wizards.com/dnd/article.asp?x=fr/pg20021106a
Outside Menzoberanzan, House Millithor's assets are a 25% ownership share of L'Tar'annen de’l Elgluth. 50% of the company is owned in secret by House Baenre and the other 25% is owned by House Morcane. (House Baenre owns many other assets obviously, including 100% share of L’Renor Vress’lve Tar’annen(translated: The Black Claw Company) and possibly secret large shares in other Dark Elf merchant companies).
L'Tar'annen de’l Elgluth owns a merchant house in the underdark halfway between Menzoberanzan and Maermidrya, four caravans, a warehouse in Menzoberanzan, and a warehouse in Maermidrya. Most of the employees that work for L'Tar'annen de’l Elgluth were selected by House Baenre, but there are seven members of that belong to House Millithor.
Alaunirra Millithor, Quertus's younger sister, Priestess of Lolth, worked at the warehouse in Menzoberanzan. Presumed dead.
Eilos Millithor, Quertus' elder half-brother, a Draegloth, he works at the L'Tar'annen de’l Elgluth house. Eilos hasn't been back to Menzoberanzan since L'Tar'annen de’l Elgluth was formed. He is rumored to be anti-social and insane (neither of which prevented him from graduating from Sorcere).
Alak Millithor, second cousin, he works at the warehouse in Maermidrya.
Belgos, Durdyn, Guldor, and Rizzen. Four Drow male commoners that belong to house Millithor. One works on each of the four caravans.