I have tested Necromancer with HOLY. Well it is hard to stuck the staff... Quote InmortalSiegfried
Necromancer ability buff units depending the target if you target a level 9 Skeleton Warrior it buff all skeleton warriors of any level permanently if you target level 9 Skeletal Mage you buff all the level 9 skeletal Mages others target buff the golem also if have another effect of increasing Necro intelligence that have a chance depending of the ability level have a 100% chance to increases Intelligence on level 1 and 100% chance to buff units on level 9 middle % on middle levels.
Didn't quite get how to buff all skeletons at one with one cast with the HOLY staff. Only golem is buffed with the heal ability and equipped HOLY stuff.
Regarding skeletons and buff with staff - new created skeletons are summoned with old stats. Or I'm missing some idea how this spell works.