What Happened the Last Time We Saw Ventress?

The last time we actually saw Ventress prior to Dark Disciple was in 2013 during the climactic episodes of Clone Wars’ fifth season. There, during the arc that saw Ahsoka Tano falsely accused of bombing the Jedi Temple on Coruscant—she eventually left the Order when the Jedi failed to support her until she was cleared of wrongdoing—Ventress had become a bounty hunter, having turned her back on Count Dooku, and survived the slaughter of her people, the Dathomiran Night Sisters, at Sidious and his disciple’s machinations.
After helping Ahsoka initially evade capture in Coruscant’s underlevels, the last time we saw Ventress in the series was when, interrogated by Anakin over Ahsoka’s recent whereabouts, she puts him on the path to discovering the true culprit behind the bombing: Ahsoka’s friend and fellow padawan, Barriss Offee—who had even stolen Ventress’ trademark dual lightsabers as part of her plans.