As masters of stealth, I was thinkin’ it’d be groovy for thieves (and maybe assassin’s) to be able to communicate with each other, while staying hidden. I thought it would work like a cabal channel except it would work by rooms. Two thieves in the same room, communicate with a pattern of gestures and such and only the thieves in that room can hear, or see rather, what’s being said. Should another thief walk in, they too would see what’s being said. I suppose it’s only purpose would be to set of ambushes, backstabs, and what not without the pain of stepping out of the shadows every time you tell or having others see someone whispers to someone every time you wanna say something. I just thought it’d be another little groovy thing that makes life interesting.