> A common trope in properties featuring the undead is that the creature believes what they believed when they died. So, in theory, if FK was a Muslim, he wouldn't give 2 shits.

And sometimes I've seen the opposite, that regardless of any gods' reality whatever the person fighting the undead believes is what can defend them personally e.g. this old X-Men comic where the X-Men face off against Dracula and Dracula is stopped from biting Jewish X-Man Shadowcat by her star of david necklace despite being undeterred by her holding up a cross earlier