Only two things made Hlethvagi happy: inflicting pain and being filthy rich.
Hlethvagi led a double life: his public face was as a warehouse operator, carter, and moneylender, but in secret he oversaw trade to Undermountain through a secret passage controlled by his minions.
Hlethvagi was the leading cleric of Loviatar in the city for a long time. Circa 1352 DR, he discovered the Long Dark Stair, a fabled and long-forgotten entrance to Undermountain. Using this exclusive passage, Hlethvagi accumulated a lot of money. With this money, he lived a comfortable life but also financed a temple for Loviatar, and finally in 1368 DR the House of Pain was completed.