I'm planning on running a game that has one of its main themes being the seductive, corrupting power of evil, where the players will see the "merits" of joining the dark side for power. Don't worry, the players have all said they would like this kind of campaign and nobody is playing a Paladin or anything that has to worry about falling from grace.
To do this, I'm going to have a dark patron that watches over the PCs and wants them to succeed for its own reasons--probably a powerful devil, but haven't decided yet. My main idea is to have this work by the patron grant Hero Points as a reward for completing tasks for her (think the faction missions from pre-season 5 PFS). The tasks are going to start out innocent enough--make sure this enemy dies or this person survives, and gradually get darker as the campaign runs on to where by the end they are actively hunting people down who have angered the patron.
So there's two things I would like suggestions of:
1: How often should they have opportunities to get these Dark Hero points? One per level/module seems like it would be too slow and so they wouldn't really see these as big opportunities to gain power (also the side effect I've seen in too many games where the players just hoard their points for Cheat Death), but too many and I could see it getting out of hand--not to mention they'd end up spending more time doing "side tasks" than the actual main story.
2: Any suggestions for what kind of things would make good tasks, and how far along? For reference, the campaign will probably go from level 1 to about 12. Keep in mind nothing should be "burn down orphanage" kind of stuff--the PCs will be staying in one region for nearly all of the campaign, and so I want to avoid anything that will draw a lynch mob (big evil things are ok as long as they can reasonably be hidden from the public eye). If all goes well I want the public to see the PCs as heroes even while they slide into evil.
If it matters, the region for this campaign is the Darkmoon vale, starting with all the modules taking place in Falcon's Hollow and going from there.