I was reading up on Leyton Hightower on awoiaf and I got this:
>Samwell: The Hightower must be doing something.
>Captain: To be sure. Lord Leyton's locked atop his tower with the Mad Maid, consulting books of spells. Might be he'll raise an army from the deeps. Or not.

So he and Euron have the same idea? I have a feeling Euron might win out since he intends to use blood magic. But we don't know if Leyton would do the same thing.