(This article is part of my original "Age of the Legion" storyline.)
Tyrant Vandaala is a powerful man'ari eredar sorceress/warrior (fallen paladin) who serves Kil'jaeden as a "replacement" for the late Archimonde the Defiler. Vandaala, therefore, commands a significant portion of the Burning Legion's military might. Her most powerful and highest-ranking subordinate, however, is a mighty pit lord named Gargonnath the Corruptor.
Prior to the events of Warlords of Draenor, Vandaala was an eredar fallen paladin who primarily took orders from Archimonde. Following the orcs' betrayal, and the Legion's incursion onto Draenor, she was tasked with commanding demons in Tanaan Jungle. However, under discretion of Kil'jaeden, she did not make her final stand in the Hellfire Citadel, like most of the other Sargerei.
After Archimonde's death, Vandaala was escalated to one of the highest ranks in the Legion, taking on the role of Supreme Commander of the Legion's military. After Gul'dan's success in opening the portal from the Twisting Nether to Azeroth, Kil'jaeden ordered the invasion of the unsuspecting world. It was Vandaala who led the charge, with her right hand, Gargonnath.