I super love this! I wasn't sure until I got to the "crowd surf" ability in your first faction, and then I was hooked. The spread of factions here makes the head spin with possibilities for heretical black masses. Imagine, for instance, an interfaith conference of Abhorrers and Avidava! Gargamox trying to suborn the Writhing Hive! Misere hiring CARCASS as security!
Minor typo: there's a "(Page #)" left over on page 45.
When I read about the "Master Maleficus," I thought that they might be a step up from a Necromancer - the pope of a denomination of black masses! In that interpretation, players might command multiple necromancers, though perhaps you'd keep the invasion rules the same, just using the placement of the individual necromancers to determine what part of your forces you use in each battle. (Like you could give them responsibility over paths from your home base??)