The party leader needs to speak to Varmunt, he will warn you about valkyrie Himelmez.
Head north and speak to Heinrich green square. This will trigger a dialogue.
After their conversation, some mobs will spawn. It is recommended to kill them for Coagulated Spells and Contaminated Magic before Heinrich kill them.
A warp will activate at the west left yellow square, enter it and start killing monsters until a message "Himelmez drains the souls of the dead" appears.
Party leader has to speak to Butcher left purple square.