Gathering storm ended, if I remember correctly, with the mandrakes and Haemonculus coordinating taking control and pushing back the tide of daemon's while the Kabals and Wych Cults were fighting each other or splitting to the Ynnari or just simply fleeing for their lives. I thought that was so epic and cool it then made me think we would see more Mandrake units in the future.
Last night I was reading the fluff I dont remember seeing much written about Mandrakes other than on their fluff page. I like how they suggest that the only beings Vect may fear are the Mandrakes and how they are untouchable in their own shadow realm atleast.
To my interpretation and memory I think it was just saying that all the Incubi were fighting the frontlines with everyone else against the daemons. It is a shame though I thought it would be cool to see a progressive story and a power shift to a new Overlord Kheradruakh or in his case King. But dont get me wrong I like Vect, Black heart is the army I play but the prospect of the changing story events were more favorable to me.
15,000 Dark Eldar