If the party enters the rooftop of Moonrise towers before completing Find Ketheric Thorm's Relic, Susdera will stop them and demand they turn back. Telling her "I go where I wish" causes her and all eight Necromites to turn hostile. Ketheric Thorm will not become hostile unless the party gets too close to him.
If the party frees or kills the Nightsong before entering the rooftop, a cutscene with Ketheric will play out. Susdera will be one of Ketheric's allies in battle against the party.
It seems that Susdera know the truth behind the tadpoles. Unlike the Zealots, Adepts, and other members of the Cult of the Absolute, the Mistress of Souls seems to be fully aware of what the Absolute is and the religious hoax they're doing.[2]
↑Despite being named as necromancers at several points, instead the Mistresses of Souls seem to be Evocation Wizards.
↑When talking to Radija, she looks down upon the party for being a True Soul, and if trying to link with her own parasite, it is revealed that she doesn't have one and she mocks the party for that. And Kressa Bonedaughter also mocks the party for that.