Here's an idea for a group plot that involves the seven deadly sins in popular myth and folklore. How about through some method, whether a magical object or a being of chaos that just wants to ruin people's lives, characters are infected with one of the seven deadly sins. So in other words, this sort of plot would need 7 willing victims, I mean characters :D where each one is possessed by the energies of a certain sin. The list is as follows.
1. Lust
2. Gluttony
3. Greed
4. Sloth
5. Wrath
6. Envy
7. Pride
One sin per character so for example character A would be infected with Lust, character B with Gluttony, character C with Greed, and so on and so forth. Now the interesting thing is, whatever sin you pick your character to become infected with has to already have had some influence on them normally. So for instance, a thief could have Greed, a whore could have Lust, an orc berserker could have Wrath and etc. Those attributes would simply be intensified to an extreme amount in the characters to become a dangerous obsession that could very well be their undoing if they do not find a cure, and soon.
So, who wants to infect a character with a sin? Come on, you know you want to...