Offhand, anyone able to point out which critters or spirits or whatever have Drain "Karma" as an ability? I've seen the other drain stuff, but the sr4 street magic notes that Karma is also a possible outcome. How would that work against non-PC characters at any rate? How would you determine Karma (unspent pool) for other NPCs?

See also: Partner/Spouse

Just kidding.

As far as mechanics go, following the example of other forms of Drain (X) seems appropriate, maybe coloured by the info on Free Spirits in SM, p. 107 ff, especially the Energy Drain (Karma) Greater Power on p. 110.

As far as how much an NPC has, how about taking the average of what the PCs have at the moment?

I believe Shedim and Master Shedim are the most common spirit/critter with this power. Imps were also able to do this in 3rd Ed from when a focus was bonded to a magician.

As to NPC karma pool - um - make it up. The players need never see behind the curtain on this one. What ever works for you. Roll a die/ dice, asign average stat, use the radom PC Karma traite (probably freaking Player whom sheet you check), average the PC party traite, Hockey scores etc

I don't mean to be trite. You control the world, revel in your POWER!!!