Shrok'lakelev arrived at Marlina's prison, they managed to defeat the Ethereal Filcher that was guarding her, Janes used Thieves' tools to cut her chains and free Marlina.
Because of her dismembered jaw, Marlina couldn't thank the group, or even explain her story, she decided to follow them on the Ethereal Plane, as thanks she would use the necromatic magic that keeps her alive as a Banshee and revive a fallen member of the party. Killing her in the proccess, finally reuniting her with Ezmeralda in death.