Cubehopper

The cubehopper spell opens a temporary door between any two cubes in the same layer of Acheron, providing quick, safe transportation for small raiding parties. The spell lasts until a number of creatures equal to the caster's level have passed through or until its duration expires. The caster can dispel the cubehopper portal at will. Leaders of Acheron's ore and goblin armies are notorious for using this spell to escape routs and massacres (providing, of course, that their opponents haven't been quick enough to cast gate seal over the battlefield).

The material component of this spell is a chip of iron from each of the cubes to be connected by the gate.

Naturally, this spell can be cast only on Acheron. Rumors abound about cubehopper spell variants that can be used to teleport between the layers of Acheron, but this is said to require a special spell key — which the rumormongers never seem to know.