I have finally learned the secrets of life and death for the first time! And I did with a completely fresh adventurer, with no gear other than the stuff he started with (a bronze mace and a bronze shield). It was quite simple actually. All I had to do was lure the zombie and necromancer mass away from the tower, and circle around the group to isolate the necromancers. Once the necromancers were isolated, they were pretty easy to strike down (although they sometimes only got injured and then went back into the mass, forcing me to drag the mass away from them and then circle around to kill the necromancers). Once I killed the necromancers, I basically kept moving in one direction and waited for a single zombie to come up to me so I could collapse it, so I could always get the first strike, and repeated until the mass was dead. However, one armed goblin zombie got a good shot at my foot and so I only barely made it through the first day. I then slept once the horde was dead, and I came back the next day more or less fully healed.
Then to my dismay I found that there was a new pair of necromancers and their minions in the first floor, so I had to repeat my dance again (thankfully, I had the good sense to go around the tower to the back, so that the necromancers couldn't re-animate the first horde again). Once I cleared them out, I quickly entered the tower and went to the pile of slabs and picked up one before the zombies and necromancers from the second floor could come down. Then I read it, and viola, Reloth Coslanaquuv (Ferriedveil) became a necromancer and master of the secrets of life and death. Coming up next: a coup d'état in the local law-giver's fortress (sadly, not a demon), and then marching an army of elite soldier zombies against the the populace of her home nation. And then, what the heck, the populace of every nation. Learning the secrets of life and death does strange things to your mind