Another idea bubbled into my head while working on Action cards specific to careers in the Career project, but didn't really hit into the themes of the careers.

The concept is Temptations are Enhance cards, like found in Omens of War or Hero's Call, which are keyed to different Chaos gods. You could have a Tzeentch, Nurgle, Khorne and Slaanesh Temptation card. The cards are used in distinct ways which enforces the theme of the god by giving a very powerful bonus. Temptation Cards may be purchased without spending points on Actions, but they have their own costs. Chaos Stars always give Corruption if you use a Temptation card, and once you are corrupted, you lose the card and the card is converted into a Mark of Chaos. While the card may be gained for free, the GM may use the cards to entice the players with power as a reward.

The Temptation cards are a little more powerful than the Marks of Chaos, representing the Chaos God's willingness to spend more energy in converting fresh blood than securing existing members.

The core theme behind Nurgle's temptations are diseases make you stronger. The conservative Nurgle Temptation gives bonuses to healing checks, but only to mask and negate penalties from diseases. As well, it allow the healer to suppress fatigue and critical wounds if a disease matches the severity of the critical wound. The reckless Nurgle Temptation is used in to quickly ignore pain and wounds on yourself, such as in combat, allowing the character to ignore fatigue, wounds and critical wounds if diseased.

The core theme behind Tzeentch is change, plotting and magic. The conservative Tzeentch Temptation involves plotting and manipulating, as long as you are attempting to undermine authority, you can use the card for social checks. The reckless Tzeentch Temptation is a magical enhance which gives easy access to magical power and quicker recharge.

The core theme behind Khorne is combat, skulls and blood. The conservative Khorne Temptation is terrible, it's designed to get you quickly back in Reckless stance. The reckless Khrone Temptation is a very powerful Enhance ability with great critical and damage potential, as well as a some Toughness and Soak increases.

The core theme behind Slaanesh is social control. The conservative Slaanesh Temptation bag of social tricks involves ignoring the shame and stress, allowing you to become a "social tank". The reckless Slaanesh Temptation allows the Slaanesh to entice others into acts of pleasure or control them with pain, giving others bonuses as long as they go along with his pleasure plans, but penalties if they do not.

Any thoughts or ideas to improve the concept?

Well first, congrats nice idea. I'm reminded of games like One Ring where Shadow takes different forms of moral corruption for different characters.

A player might have to choose "which of these whispers do you start hearing" on getting first corruption point.

that's a GREAT idea.

Great idea, but it may be one of the things players end up not using because of the risk. It is a conscious effort as I read it, meaning once you use this, you have willingly corrupted yourself, which is entirely different than getting corrupted against your will and good intentions. It's a great idea, but I don't know how well the idea of heroes asking for assistence from chaos gods in secret fits the warhammer theme to such a degree that it warrants a game mechanic.

I think this mechanic is an interesting idea but only as a hidden mechanic for the GM. I do not want my players to just "game" the chaos gods as some form of buff. But I am in favor of hidden mechanics anyways like tracking player health and so on in secret because it is just weird if the players have too much information. "The enemy is X which I know has always around 10 WT and does 2 dmg to my character so I can just stay in combat because he will die before dealing more than those 2 wounds"

I think this mechanic is an interesting idea but only as a hidden mechanic for the GM. I do not want my players to just "game" the chaos gods as some form of buff. But I am in favor of hidden mechanics anyways like tracking player health and so on in secret because it is just weird if the players have too much information. "The enemy is X which I know has always around 10 WT and does 2 dmg to my character so I can just stay in combat because he will die before dealing more than those 2 wounds"

It's not unrealistic. When fighting you do actually have some idea of the opponents health level and especially when fighting with lethal weapons, the wounds may be visible. Knowing that you've given a human 10 wounds, gives you an indication that he's in a bad spot. You won't know exactly how many wounds he has, but you will certainly have an idea about how hurt he looks. That doesn't mean his next action won't knock you out - but you would be able to tell that he is in fact hurt.

While you can hide the wounds the NPC's have recieved, I find that even more unrealistic. If you hit someone in armor and the hit penetrates his soak/toughness you should be able to have an idea about how much you hurt him. While you can as a GM try to hide all this, I think it's mostly a pointless exercise, as the game system is just the underlying mechanics and players role play despite mechanics anyway. So if they know that 7 wounds went pas the targets soak/toughness, they will know they had a solid hit. No need to mention the wounds in role playing - but they will know they inflicted a solid hit and the actual wounds suffered by the NPC is just an easy way to convey the amount of pain they inflict on the NPC. While having such a precise measure of the pain may be unrealistic, it's just an abstract layer, that players ignore when role playing.

I just hate the level of detail because it encourages bad RP. If you say to a player "You have 5 Hp left." she most likely won't change the way she plays the situation but if you say something like "Your vision gets blurry and you struggle to not fall." the player will change his actions. And that is what I actually want.

Including too much information just seperates the player from the character. I give players an idea what the situtation looks like but I want room for interpretation. Otherwise you get these weird D&D moments where combat just becomes a war game where you crunch numbers.

I see it from another perspective. Instead of supporting players role play you force them into your vision of how wounds affect them. Knowing they have only 5 wounds left until they pass their threshold is an RP invitation for the player, not the GM. If you take this away from your players, then they'll never get it. Besides in WFRP most characters can take one two or three hits before going down and knowing the wounds they have will make players think twice and react according to their wound level - unless they do want to go down. I can only imagine if you were in a fight and you'd have to rely on someone else to narrate to you what your wound level is - weird :-)

I think as a GM you should give your players the power to use the mechanics and everything to RP, or the mechanics will just get in the way and another system may be better than this.

I also roll all checks in combat and otherwise (unless it needs to be secret) out in the open. I do this because in combat and social situations you have a **** good sense of your opponents ability - the dice pool is just a straight forward measure the players can react to and then translate the thought of "wow the troll has 9 strenght" into, "that troll looks unnaturally big even for a troll - be careful now". If you take these opportunities of RP away from the players I think you give yourself a lot of extra work, while actually removing a layer of playing from the players.

Having 5 wounds left is just so insanely gamey. Same with knowing that the enemy has 9 strength or 2 ranks in weapon training. I am not trying to run a simulation but knowing exactly how many hits your character can take is just way too unrealistic for me. You can ofc use the information of having x HP left as an invitation for RP but why be so specific? The wound system of wfrp3 is really bad anyways without being able to bleed out, not being able to die from normal wounds, instant healing over night and so on.

In addition you might know your enemy is strong or skilled with swords and I even tell someone who has mastered the weapon skill the exact level of the enemy after taking a look (because she is actually able to read the minor difference between certain levels of skill) but why would the scribe know how good the opponent is in handling weapons?

Yes I do force them "into [my] vision of how wounds affect them" but I also force them to see the world as I describe it and so on. After all describing stuff is what the GM does and seeing as I am me and not someone else it will always be a description of how I perceive things.

Afterall I do this in all systems and all my players say themselves that it is better for them. This will of course differ from group to group but mine were always okay with it. In the end it just depends on you and your players and how the group wants to play. I just happen to play with people who play the same way I do (throwing out mechanics that slow the game down or hiding information that is just too gamey for our game etc). Playing with others that want something different out of the game will not work well anyways so you just have to look at the group/situation.

I just hate the level of detail because it encourages bad RP. If you say to a player "You have 5 Hp left." she most likely won't change the way she plays the situation but if you say something like "Your vision gets blurry and you struggle to not fall." the player will change his actions. And that is what I actually want.

Including too much information just seperates the player from the character. I give players an idea what the situtation looks like but I want room for interpretation. Otherwise you get these weird D&D moments where combat just becomes a war game where you crunch numbers.

I think this depends on your players. I have found players who do not change their actions whatever information you give them, and other players who would change their action if they find that they have only 5 HP left.

If you want to get away from HP altogether then have a look at what FFG have been doing with 2nd edition Dark Heresy. Not perfect, but it may suit you better.