Each boxed set (Lure, Winds, Signs and Omens) has cards called Marks of Chaos unique to each dark god. Um…when do I use these?? Anytime I want to slap them on a "boss" monster?

Pretty much. If you want a character/monster to be particularly dedicated to one of the chaos gods, give him the mark.

Lets not forget that the Chaos Gods can "gift" it to someone who has drawn their attention. You dont get to choose to get The Mark, it just kind of happens. Your bloodthirsty warrior may have drawn the attention of Khorne and may wake up one day with a funny tattoo on his skin resembling the Mark of Khorne. Give the PC The Mark and let the slow corruption build up begin.

The Marks are used as a boon from the Choas Gods. They make the bearer more powerful. But for a PC, that boon is also a bane because it marks their inevitable decent into madness and mutation.

Gitzman

there are ceartin monsters that already have the mark of a chaos god by their definition, the most memorable to me has recently been released in hero's call, names "archaon the everchosen" or something like that. he has all 4 marks ;-)

and i recently gave a mark of khorne to my dwarf slayer, who had seemingly been begging for it in his actions….that makes for a campaign in which he is now trying to get it treated, which might even be possible somehow….lets see.

i think it states in the books that the marks are not meant for players, but i could be wrong on that. however, giving it to a player and having the character even find out what he got there is hilarious

I think the marks are very much meant for players (and monsters if needed). They should be treated in a very similar way to a mutation in all regards. They draw the same kind of "OMG ahhh" from the populace and are grounds for lynching in most cases.

Picture some guy you tackle in the dark alley and discover he has some strange tatoo on his wrist or shoulder. That is the mark. It can be subtle or very obvious. Some wear it willingly and others not so much.

PCs who gain a mark, marks the first steps towards corruption, not to mention the attention of a chaos god. It will become something the PC is forced to hide at all times lest he draw a lot of unwanted attention from Witch Hunters or paranoid townsfolk.

I would also suggest that the player who has a mark gains a corruption point every week or month or so to represent the slow corruption building within him.

Gitzman

Of course this is a personal opinion, but I rather think a Chaos Mark is more a reward for being very devout and have successfully accomplished the commands of a chaos god than the first step to corruption.

If it would be like this all the cultist will have the mark while they do not. Also I can recall than in first and second editions of the game, chaos mark were rewards only given after the servant was proven worth it.

But again, this is only my view.

Yepesnopes said:

This point of view also works really well if the player characters are evil chaos worshippers. Working to gain a mark of chaos could be an epic adventure in itself.

But everything above makes sense to me, there are multiple ways to utilize the marks of chaos.

I think i've always enjoyed the idea of an unwilling pawn in the Chaos Gods plans. Someone who may not want the mark but had it bestowed upon them because of something they had done. They are then forced to deal with the concequences, hiding, lying, etc, or give in to the taint and move further down the path of corruption.

Gitz

I've been considering the following house rule for corruption and marks of chaos:

When using corruption to add a difficulty die at a narratively dramatic moment, the gamemaster may narrate how the character feels the lure of the chaos powers, offering their help. The character may accept the influence of chaos (narratively specified as belonging to one of the chaos gods), and add an expertise die in stead of a difficulty die. The flip side is a permanent, irremovable corruption, tied to the specific chaos power. When the character reaches 6-WP such permanent corruption points (the Chaos Gods bestow their favour more readily on the strong), they receive the appropriate Mark of Chaos.

Forcing the choice between hindrance and major help at crucial narrative moments can really give the kind of slide into corruption that is believable, I think.