Alright, my friend dreamed this up, and I figured I'd post it for her, because it's somewhat less awful than her usual ideas.
Basically has no weapons. Only a cloak that last twice as long as a Spy's, and recharges when they hold still. High tolerance for blast damage.
Their purpose is to sneak around the field, and plant stealth landmines in the ground that blow up anyone on top of them.
So it's basically a stickyDemo, only you can't see the stickies to avoid/destroy them.
I personally would think this class would be a pain in the ASS to play against, but like I said, it's one of her less-worse ideas, so I figured I'd let her get some feedback.
She also had one that was basically a Scout with a flamethrower, but I just said FUCK NO, because it would be far too OP.