@Piqueniale When you turn in the last heartstone piece the guy tells you what to do but it's not technically a quest so it doesn't show up in the quest log. It's easy to miss. But you have to go down in the most southeastern corner in the red castle area. Not the entire map, just the area with the red castle right down where that un passable line of bushes is. You have to kill the big overlord guy or whatever. Assuming you sided with the alliance. If you were with the shadow runners I can't imagine it's too different just look around that area for the big final boss guy.
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