Black hand is a recurring theme in Ptolus, which is why I decided to create a model of such. In addition, it can be used to present various spells in D&D 4E as well as 3.x rules, and possibly in other rpg's too. And when trying to find more use for it, a subterranean hand that grabs people from the surface sounds quite mean...
Shape of the hand is created from a wire. Art studies help when doing this, but you have always a good model attached to your arm, from which you can check the right posture and scales!
When the wireframe is ready, I've glued pieces of paper on each side of the palm, and wrapped another piece around the wrist. Then PVA glue is applied, layer after another, to fill the gaps. If there are extruding pieces of paper after a few layers, go ahead and cut them off.
Filler powder/PVA glue/water -mixture is added on the hand, again in layers. The hand in the above photo is glued on cardboard & styrofoam sheets.
And here the hand is ready, painted with matte black, as part of dungeon decoration. You can use some blue drybrushing if you want to give it a bit more shape, but I decided to go with plain black.