During the course of the War of the Spider Queen, Vhaeraun died but his church didn't collapse, at least not completely. Followers who didn't believe or simply didn't know about their god's demise continued with their prayers to Vhaeraun and these prayers were answered, though none knew by exactly what. Whatever answered their prayers, it gave the Vhaeraunites their magical powers. Divine casters regained their spells and lay-worshipers also gained some minor abilities.
For the drow, the post-Spellplague era was a time when Lolth's rule was almost unchecked due to the competition being dead. The church of Vhaeraun continued their opposition work while another religious alternative to Lolth was Ghaunadaur.
As a general rule, a skulker of Vhaeraun's abilities were directed at getting into places and coming safely out again, or they revolved around poison.
All skulkers were able to increase the power of applied poison with an ability called skulker's venom. With increased skill, they trained themselves in the art of stealth and acrobatics with the intent to break into their enemies' houses. The most accomplished ones trained themselves in the skills to drop the offensive capabilities of enemies who were victims of their poison.