If you're using a region of dreams in your campaign - Dal Quor in Eberron for example - the Lucid Dreaming skill from MotP (page 203) might be worth looking at. It's pretty much what it sounds like. Various checks of varying difficulty let you realize you're dreaming, change various aspects of your dreamscape or yourself, and stuff. Then there's the applications that let you visit someone else's dreamscape, essentially appearing in their dreams. If you grapple them there and make a DC 25 check, you can drag them into the "Dreamheart". In the dreamheart, not only, does everyone take 25 damage per round if not taking shelter, if you die there, you're dead for good - as opposed to dreamscapes, where death is just as fake as everything else. You can, of course, use all equipment and powers you have at your disposal IRL. The best part? After you're done killing people in your sleep, none of your resources IRL are expended. The skill does require a fairly obscure alternate cosmology, though. Dal Quor in Eberron, as mentioned above, is a perfect fit, but requires some adaptation to work with the rules in the section.
