If Isolde thought being Severin's prisoner was worse than hell—more painful than death—then being Lucien's prisoner was beyond that.
She never expected Lucien to treat her this way. They were supposed to be on the same side. They both hated Severin. So why was she the one paying the price? Just because Lucien's sister died at Severin's hands, did that mean Isolde deserved to die at Lucien's?
Did Isolde kill Renata? No. Not. Isolde didn't even know what resemblance she supposedly had with Renata—she had never seen her, not even in a photo.
Lucien approached her, pretending to be a saviour, offering her a way out—a chance to avoid watching her mother rot in prison.
Lucien gave the orders to Liraine and Ivan to make Isolde appealing to Severin—so Severin wouldn't kill her too easily.