I'm making a NPC with competing familiars for a campaign I'm going to GM and had a question. He has in 7 levels in Magus as a Bladebound Soul Forger and 2 in Souleater. The idea is that he's a literal soul forger, imbuing his arms and armor with the life force of other creatures and in some cases souls. Needless to say, he's an evil NPC and I'm going to have some fun seeing if I can trick the PCs into collecting souls for him to use (and share with a Fiendish Vessel devoted to Szuriel). Anyway, I've run into a small problem.
Black Blade (Ex):
At 3rd level, the bladebound magus’ gains a powerful sentient weapon called a black blade, whose weapon type is chosen by the magus (see sidebar). A magus with this class feature cannot take the familiar magus arcana, and cannot have a familiar of any kind, even from another class.
Cacodaemon Familiar (Ex):
At 1st level, the souleater gains a cacodaemon familiar, as if she had the Improved Familiar feat. If the souleater already has a familiar, the cacodaemon devours it (which does not penalize the souleater). The souleater counts as an evil outsider for the purpose of utilizing cacodaemon soul gems.
While the obvious thing would be to just drop the Bladebound archetype, it's not an option in this game. One of the house rules for the game is that any Magus needs to be either a Hexcrafter or a Bladebound, due to previous events that occurred in the setting.
Should I just change the fluff around a little bit and say that the soul inhabiting the black blade was a cacodaemon working to corrupt the NPC and create weapons for the baddies on the material plane?
It's not the most elegant of work-arounds, but since he, by RAW, won't get the familiar, you can always give him the Spell Blending Arcana set to Summon Cacodaemon, allowing him to summon a single cacodaemon for rounds/level. Obviously, this is still rather restrictive, so such a character may be likely to try to take opponents alive so that he may kill them and harvest their souls at a later date, when he's able to devote more slots to cacodaemons, rather than combat spells. This can actually be more effective than a simple cacodaemon familiar, as a single cacodaemon can only "process" a single soul per day, but multiple castings of the spell allows for summoning multiple cacodemons per day, allowing him to collect multiple souls per day.
This reminds me of the Blackrock Blade from Ultima VII.