For my monthly group i have written a series of adventures and played some of the FFG modules. Now i want to try my own bigger adventure in a self designed city. One of the plots in this city will be an extreme shallya priest, who wants to heal everything, including mutations. On this extreme and not sanctioned way he has build a group of like minded priests and aides around him in his little temple. This hospice was a part of a greater one but is localized seperatly from the main temple on a small island. Before he seized this building it was an asylum.

Now my question. Is it possible for this priest to have the mark of Tzeentch and still curry favor from shallya? Can he use normal and divine magic at the same time?

I know this is a bit of a cop-out answer, but I'd say it really depends on you. What works for your game and for you.

I would say that the grounds for allowing it are that Shallya is a forgiving God, Tzeentch is Nurgle's worst enemy (also Shallya's worst enemy) and that you don't have to say that everything happens instantaneously. In real life, people don't get 'insanity cards' that suddenly become active, they just go a bit mad (or a lot mad). So your Shallya priest, with the best of intentions, is doing his/her thing, healing people as Shallya wants...

But that doesn't have to mean that Tzeentch can't also take an interest and 'reward' the character.

You might also like to have it that the character can't use both at the same time (and perhaps might not understand exactly what's going on, not realising that they are casting magic, and think that the 'cleansing blue/pink fires' are actually a Shallyan miracle).

Or perhaps the Shallyan priest got as far as they could with blessings, but for really serious health problems he/she has to go one step further, and so only 'activates' the mark of Tzeentch when he/she is doing something very extreme (that Shallya's spells won't help with).

Perhaps also, Shallya gradually withdraws her blessings - in warning/punishment - but the priest finds him/herself becoming more and more reliant on magic to help/cure people.

The case against is that it sets a precedent, but that's not necessarily a problem. There are plenty of 'one-offs' after all.

It does though force you to answer some questions about the nature of the warp/the realm of chaos and the nature of divinity! Which for the most part, in most games, can be hinted at without having to be explained. You may want to decide though how active an interest the Gods take, how much they intervene, how bothered they get that other Gods are interfering with their followers...

Interesting question.

Thanks for the answer Angelic Despot, despite of the "cop-out" I am aware that i can do in my game world what i want, but i want the situation to be comprehensible and the NPC´s Motivation not GM given but developed. There is nothing more what i despise in the written adventures of WHFRP than not traceable reactions of NPC´s and GM given Situations without any logical cause. For all WHFRP 3rd adventures this demanded some corrections as i GMed those, apart from eye for an eye.

That is why i wanted to know some opinions of fellow Gamemasters. He willnot use both powers at the same time. With the Tzeentch spells he mutates his victims temporarily to monitor those changes and learn about mutations, after what he uses his goddes gift to heal his patients.

For the concept of my world divinity is just another (safer) side of magic and the gods are just aspects of it like the colours of the winds of magic. In my "old World" no greater force leads the human race. They are alone in their fight against their darker side (Chaos).

If divinity is part of magic in your world, then istm it would be pretty easy to say that the priest can continue to curry favour and channel power. It would just be matter of meta-physics about where the favour come from exactly. If the priest still believed he had the favour of Shallya then I would use that as some sort of plot hook whereby Tzeentch is corrupting what the priest does and controlling the favour so the priest is effectively doing Tzeentch's will. If the priest has forsaken Shallya and is all-in with Tzeentch then he will be praying to Tzeentch (or a deliberately Tzeentchified version of Shallya) knowingly for his favour.

Either way, I'd add a line to any invocation, like: [Chaos Star]: Target suffers one Corruption

You can of course take "your Old World" the direction you want, but going by rules, Liber Mutatis page 10 states the mark is for "loyal servants", and page 20 continues in the same theme for marks of chaos generally. Liber Infectus when speakng of Mark of Nugle also states "reserved for his most loyal" (page 9).

So it seems to me this would really be a "former Shallyan" or "false Shallyan" now getting their mojo from Tzeentch.

The Shallya hates Nurgle and Tzeentch doesn't like him either angle is a good one to explain some cross-over or drift, attraction, though all would be part of some grander scheme of Tzeentch's against Nurgle though likely at expense of Shallya.

If you do go down the route of Tzeentch vs Nurgle - Shallya vs Nurgle, it will not be implausible that Tzeentch grants it's mark to the priest.

One thing about Tzeentch is that he is the Bringer of Change, and his machinations don't always solely work through the cults of chaos. When the opportunity arises to introduce Change to an existing situation, I personally feel that Tzeentch would seize it.