Crion_dm459
A setup like that already doesn't go well. The Paladin would try for his detect evil, and it would always go off and he would get paranoid.
Also, the normal pally would try to stop the anti-pally from doing what he does best.
I don't think the "Dark Paladin" he described is Evil, just Chaotic. He didn't mention the Good requirement changing. So they're not total opposites...
I personally don't understand the logic behind this, since a paladin is supposed to be upholding the law... so how can you have a chaotic one? Baffling. Then again, I don't know the details about the class...
If the "Dark" Paladin is still designed to be protecting people, then you could have a brawl break out or some crime occur in the city they're both in, which they both end up trying to stop... and then have that crime be tied in to your major plotline. That way the characters sort of meet their main challenge almost immediately, and are given a reason to band together.
If I'm completely wrong about the "Dark Paladin" being Chaotic and he IS evil, well, then I think Crion is right and it's not going to work. At all. One game I was playing in, our party was good, and one of our members decided to join a clan of evil people secretly, and he ended up hacking another our party members into bits and nailing his pieces to trees around the forest...
Evil and good don't mix. Unless the evil creature is needed by the Good people and is in their captivity, or trying to manipulate them or something. Think of Gollum - while he's not entirely evil, he does have a conflict of interest with Frodo and Sam, and this does lead to conflict between them.
Anyway, good luck with your campaign ^_^
*edit* Oh, didn't realize you figured it out before I posted that
sweatdrop sorry! Let us know how you're working it... or at least tell me if I was right about your Dark Paladin being Chaotic!