Hey the King had a daughter, hell whatever age she is, even if she is three, put her in power, all the more funny if we do that. Her 'council' of nobles will all be puppets to us anyway as well as she. But just in case, let's put a bit of corruption in her. And hey best-case scenario, we may have just found a playmate for Alyshtr or something like that.
hell yes!
Kill the mages, puppet government (with king's daughter on throne if she is under 10. if above 16, consort bis, second demonic daughter ), accept/enslave soldiers.
Next target is Culloden. Use the Titaneghoul there once it has recovered. RAZE IT TO THE GROUND. meanwhile, corrupting Dolnar and other cities.
If 11-15, consort for Nameless. "So, I heard how you like the after party. I saw this, and thought of you. No. You can't let it free. No. You can't give it away.". Heh, that would never work. Suggest 15 or younger, puppet, just to round it out.
We should try to get everything BUT Culloden. Once we have the weight of Barrtal behind us, we'll have enough human soldiers that Culloden won't have enough good to put every single one of them down.
On the idea of playmates for Alyshtyr.. if we find an infant son/child son of the king, we can secure blood legitimacy of Barrtal("Yes daughter I am marrying you to this child. Yes I am aware you are possibly too young."), and hey, the kid would grow up in good(evil?) hands.
We should infuse our lands with evil, so that our most devout(like, THE MOST devout, the top 1%) worshippers slowly take on attributes relating to us, like, for example, unnatural blue eyes, flame-like hair, useless vestigal extra arms, that kinda stuff(and maybe items(which are evil-ized, like weapons/torture tools/idols to us, stuff like that) are twisted slightly? I dunno, maybe just magic ones.).
We should offer Dal'Kahh the option for a beneficial mutation(provided he doesn't go insane from it, or die), as a reward for his service, extra arms, special uber-eyes, flame hair(ala Needles Kane)?