The Acts V: Reaper of Souls #2 The Black Soulstone

in the hell any demon putting it on their flesh would become Diablo, the stone is a powerfull cell but if the cell is thrusted into something made of flesh all the demons would use the body as a vessel and roam free once again, the only way to control the stone either hiding it where no one will ever find it ( proven to fail miserably) and controlling it with a more powerful will ( as Malthael does in the intro of RoS)