The idea was actually posted by DC on the other board, but it seemed like a fitting utility skill for orcs, so I figured I'd pass it along here (with some modifications):

'Heightened sense of smell' which would allow orcs to sense/smell unseen (N)PCs (hidden, invis, duo, maybe camo) in the same room. They would only get an echo that Someone is there ("You sniff the air and pick up a scent that seems out of place here." or some such). Probability of detection would increase with each passing tick (~mid-tick?) that they are both in the same room. The skill would also have a timer, so orcs would have to choose when to use it and not be able to keep it up all the time.

Also as a means to counter it maybe also give trannies or air path invokers some kind of deodorant spell :P that would neutralize all smells.