Aaron said: Dynamic lighting and line of sight would let you hide them, but we probably need more info for a better answer. Like what? Jacquesne J. said: Shandrick, major props for trying that type of campaign. My head hurts just thinking about trying to keep track of two separate parties of PCs, working hidden from each other, plus all the NPCs that each group is interacting with. You're basically running two separate campaigns at the same time. I have a decent amount of GM experience but I wouldn't even attempt something that complicated. Good luck, let us know how it goes! The closest I've come before is that at the start of the Campaign, I told a PC he is actually the bad guy, made sure he sat next to me at the table for ease of note passing, and told him to do whatever he wanted. It was an epic game. I agree, this may be tricky to try, but I'm willing to give it a shot anyway. If it gets too much, I'll just get the evil PCs to swap to a new day and run their session before I run the good PCs.