Balsha was a heretic!!!!!
The fact that the morgathian church uses what power it does in a subtle fashion can indicate many things. Here is my list of reasons; (outside of it balances the world/game of course) which are interchangeable and accumalative if you wish, I do not ahere to ALL of them in my P-Harn.
1) It is Morgath's will. He is insane so we cannot guess his reasons.
2) Morgathian clergy are conservative by nature; they are waiting for the right moment.
3) Morgathian clergy are not conservative by nature; but this Gurim is..and he has been at the reins for a long while.
4) Meokolis commands that the right moment be chosen.
5) The general political situation is ripe, but the tools are not. Either schism in the church or an undersupply of 'Gulmovrin' lead to a rational assessment of failure of Harnic domination.
6) The general political situation is ripe, the tools are good, but book-keeping is bad ('C'mon..you forget where you put stuff when you are a thousand years old). This leads to an incorrect assessmnet of success/failure.
7) Fear of failure; The Other nations/gods are too strong at the moment. This could be reasonable (i.e they have effective countermeasures) or paranoia: (i.e. the Gurim believes they have effective countermeasures.)
8 It all sorted; it is happening TOMORROW
9) Zombie apocolypse is not the goal of the church. It is in fact an arcane fraternity concerned with keeping a few corrupt individuals living the thirteen lives of riley. Drawing attention to this is not a good idea.
10) The shadow/zombies does not exist as Canon. The church is a faith community (albeit a bit dark) which encourages the concept of the mystical undead (perhaps with zombie practices similiar to Terran ones..it is not voodoo is it..whatever it is called). half a dozen stoned guys in tattered clothes might struggle to take over the world.
11) Zombie apocolypse is happening...but not on Harn. Perhaps in Dalkesh, Kamerand, Mernat etc the church is covering the world in darkness..with Golotha as a supply port.
12) Waiting for an 'auspicious' moment. The real stuff is ready...just waiting for that comet
13) The 'zombie' apocolypse is an 'amovrin' apocolypse. The kings of all the nations and guildmasters are all secretly undead...