Usually I don't get involved in these conversation, this one interests me because it can be handled so many ways.
Whenever I read about the Unlife attempting to gobble up the Essence (Existence) I think Terry did several years of Tia Chi. The entire Battle is like the spiralling of the Ying and Yang.
The Unlife as we know it is a single idea, driving itself through the bowels of creative. Attributing an alignment to it is the same as saying your Car is Good and his Motorbike is bad. I always saw the Unlife as the Distilled Child of Entropy.
If you will, think of the Universe as a Large brain that we are all part of. It has two primary thoughts; Existence and Nothingness. In the game Existence is ancient, slow and almost pondering. Nothingness is fleet, hard and decisive.
At this points different Schools of Thought exist. Some think the Roles are turned, that Creation is the Enemy of Existence and that Nothingness (the Void) is sleeping it's way across the cosmos gently absorbing the mess of Life.
In a Human way of thinking, the Unlife is more a focused Stream of Consciousness. It has a single goal, to return the Universe to a Neutral state, by removing all children of Existence. This goal is antithesis to the ?Human Condition.? I presume that in many cases all living thinking beings will have a sense of survival. So when a Mortal Mind is ?blessed? by the Unlife they start to comprehend It's cause. When the Unlife begins to ?control? the mortal it is more along the line of emotional focus. Eventually the Super Ego is replaced by the Unlife and the PC becomes a NPC.
At that point the NPC is ?Evil? or my personal favourite, ?Truly Evil?. Not because they are Truly Evil but because they represent EVERYTHING we fear and in many cases refuse to understand. We call them evil and they are in truth a part of a Natural Order.
Suffice to say that we as Players do not want that Natural Order to dominate. As beings connected to Existence, we instinctively fight the Unlife. In truth we are Pawns of a larger game, a simple battle between two opposing and necessary forces. This is not Order and Chaos.
So when you come to the ideas of the Unlife, it's Theology, you are really just questioning the Beings that Work for it. Keep in mind that Power Crazed Men, Women, Elves and others tend to be creative thinkers. After 5000 years of reading, experiencing, doing and finally putting plans into action, can create one hell of a villain. Success and failure boil down into a stew of reason that can only lend itself to brilliance. To add to that individuals mental prowess, they are plugged into the over whelming experience of the Unlife. The force is made up of trillions of past lives, billions of worlds destroyed and an endless archive of sneaky plans.
To add a bit more detail to the madness, imagine the endless voices, ideas, ravings and loss of the members of the Unlife. It would never stop, sometimes it would be helpful, others detrimental.
I am a Priest Arnak...
Who the Priest is working with decides their approach. When they go into a city, citizens expect and need a structure and a face. People want to see a pretty God that represents their desires, revenge or hates. Sometimes they want a god that presents hope and faith. All perfect tools for the Priest. They teach their dogma and change the way people see themselves, their friends and family, leaders and the Powers that Be. The priests don't have to convert an entire community, just a few of the more respected individuals. The rest will follow.
When approaching the poor and weak they come as holy men. They can dress like any one of the known Faiths and never say a word about their God. People will presume they are what they present themselves as. When the village asks for help the Priests give it. They pray, in a none committal way, and incite new ideas into a structure that is thousands of years old. Words like Freedom, rights and self awareness are not words that the Current Leaders want their followers to think about. This leads to conflict and that leads to confrontation and eventually revolt. Leaders are forced to put their peasants back in their place, and that simply creates more division.
Words are powerful things. Give the right man hope and you create decent among the farmers and common folk tired of starving so that their lord can live and grow fat. The people are already angry, a priest just needs to give them a bit more hope and direction. ?Your God is With you!?, ?You will not fail because we watch over you.?, ?Wait till the time is right, we will tell you when. Watch for our signal.?
When confronted about their faith, which God they follow the Priest would answer with ?I follow the Wind and the Sky, the Sun and the Moon.? or ?My faith is for those that believe, not those that must question because I am different.? Say the latter in front of a room full of poor people, when the big wealthy adventurers are questioning the poor Priest.
I think that truth is one of the most powerful details of the Dark Priesthood. They don't have to lie. Their faith is about Freedom and Faith. I would say that a great many of the Priests do help and offer hope. My own party has been healed by a dark priest, and they had no idea, the party assumed she was a follower of Orhan because of her cloths, but no one asked.
Wondering priests would wear practical cloths, with the colours of the faith they want to behave like. They would have a different Holy Symbol stating they are part of an ?Older Order?. The priest in the city would dress to impress. Their temple would also reflect that view.
A priests word is his life. Tell the truth, the hard truth, that makes men turn away. Try and keep things general;
?Those Elves, all that understanding yet they refuse to help.?
?Damn those Loremasters, if only they had helped when you asked your crops would not be dead now. Let me show you how this is done.?
?Your leaders grow fat off of your lives, just look at old Pak, died in his field, worked to death so some nobles brat can go and learn to be a better tyrant.?
Unlike a Death Cult, there is no immediate doom. The Priests don't have to give a time and date for the end of all things. Also unlike a Cult, the villagers can and will still interact with a ?Normal? priest of Orhan. In truth, as stated before, that only helps the Arnak cause by telling people to get into line, bow their heads and be good sheep they reinforce what the Arnak Priest said.
By following this idea, I have had players convert to Arnak. They never fell to the unlife, because the Unlife doesn't need them to. It just needs them to act when the time is right. So the priests wander and preach and help and subvert all with the truth. I at least try to keep the Lies to a minimum as the Detect Lie skill and Spell are always handy.
I don't think I covered all the topics here or how they may function but that is how I work mine. Just my two bits to a very interesting topic.