The DFRPG rules for power sources assume that each power source has an actual entity (or proto-entity) of some sort that guides/restricts its useage. I don't know if that is entirely accurate to Jim Butcher's concept of Kemmlerian Necromancy -- I had been under the impression that it was more of a cult that had learned certain methods or techniques for applying magic (in seriously Lawbreaking ways).
Assuming, however, that Kemmlerian Necromancy does qualify as a power source -- and therefore has some sort of entity controlling it -- how should it work, and what should its agenda be?
First, I'd assume that KN's source is either (a) some sort of ancient spirit that Kemmler discovered and struck a bargain with in order to gain power for himself, or (b) a spirit that was 'born' out of Kemmler's accumulation of power (or possibly out of the release of power as he died). This spirit wants to increase its own power or accomplish some goal (destruction of all life, for example), and it's willing to 'invest' some of its power in order to achieve some later windfall.
As such, I'd stay away from agenda items like 'accumulate personal power for the power source user'. This may be a means to one or more of the source's goals (because more powerful lackeys might assist in achieving goals), but it isn't a goal on its own.
Here's my take on KN's goals:
- Weaken (and ultimately break down) the barriers between life and death (this allows KN to exert its power more directly)
- Sow fear among the living (because KN can feed on fear)
- Sacrifice life to KN (killing mortals through KN feeds the power of their life-force back into the source)
- Ultimately extinuish all life, replacing the chaos of the living with the perfection of death
If KN is actually an embodiment of Kemmler himself, then a goal such as "resurrect Kemmler" would make sense. But I'd favor KN as a dark spirit that Kemmler sought to partner with over KN being Kemmler himself.