I use this art like the vampires use protean. Except with shellslide, you can move through alot more things. Want to rob a bank? Slide from the outside of the wall right into the vault! You get the idea.
After successfully shellriding a large object such as a car, a wraith may slide to a different side of the object and come out. This may not be done on liquid, gas or organic material.
Roll dexterity and inhabit difficulty of seven. Sliding to the roof of a building would require more successes than sliding through a wall.
If the shellslider wishes to travel a long distance over something such as a road, treat each success on the dexterity and inhabit roll as ten cubic feet of movement. If they wish to travel farther than that, they may spend a pathos point to be able to travel anywhere on the object after making the dexterity and inhabit roll. The wraith only moves at a speed about as fast as it can run. (about ten cubic feet per turn)
In order to transfer to another object, the wraith must first shellride it and then repeat the shellslide process.