|There are two battles during this quest. They both take place in Swiftperch, and are separated only by a menacing cutscene.
Both Ryssfloh and Glazrael must survive the fight. Glazrael is rather weak, so use heals and try to pull aggro as needed. Ryssfloh is tanky and shouldn't need any help.
During the first battle, it is best to ignore Baenryss. Ryssfloh will hold his aggro without fail. Instead, follow Glazrael, attacking what she attacks. As groups of lesser mobs thin out, she directs her attention to Baenryss. Take the opportunity to help heap on the damage. If she switches her focus back to a group of mobs, follow suit and help her as before.
Once Baenryss falls, a cutscene will play. Afterwards, there is a fight with the Masked Mage. He will summon a big, gnarly looking mob. Luckily, it doesn't hit very hard. Take it out first. Y'shtola will then join the fight, and the Masked Mage will fall quickly.