[@Severe Triage], I await [@Zahrale] before mine. Also probably for Hades to reply as well. Possibly.

Although the key to winning this war will be first to drive out the Romans from Egypt and restore proper worship of the Egyptian Pantheon. To do this, Thoth is willing to sacrifice a good number of Egyptian mortals to suddenly die by some catastrophe he creates, such that there is an imbalance in the flux of souls into the underworld, which will allow him to exchange the souls of Egypt's ancient warriors as an undead army. 

To avoid an all out god-war, all this of course is to be done by a proxy. A mortal patsy who will conduct the necessary rites and rituals to summon forth said catastrophe and raise the dead. Osiris as lord of the Egyptian underworld will have the final say on the souls being release or not, but the promise of even more Souls, Roman souls even would fulfill the void as Thoth will work towards rechanneling the souls of all those who die in Egypt to Osiris, rather than Hades, thus starving Hades of power, to the point where he may need to plan a traitorous plot against Zeus and friends. And for that, he would need to implicate Morgana...