The Soul Urn is an advanced item central to the Age of Steel. A Soul Urn, as its name suggests, is a collection of souls confined to torment inside a simple piece of pottery. Their suffering may thus be conveniently harnessed to create various devices and tools to make Steve's life easier.
A Soul Urn may be thrown, if one is feeling particularly cantankerous, though violently releasing ghastly forces might create some problems. It may be possible that Steve could channel this energy into a pumpkin - provided Steve has a good aim.
The process of creating a Soul Urn is not trivial, and begins with the mining of large volumes of Netherrack. The Netherrack is ground in a Mill Stone (preferably some distance away from one's location), and eight pieces such Ground Netherrack or Soul Dust are passed through a Soul Sand-filtered, mechanically powered Hopper with an Urn placed directly underneath. That the Hopper be powered is critical, lest too much evil coagulate inside it...
An important by-product of Soul Urn manufacture is Hellfire Dust.
It may also be noted that Soul Dust (obtained by sawing Blood Wood) can be substituted for the Ground Netherrack during creation of the Soul Urn. Mundane Saw Dust will replace the Hellfire Dust as a by-product if the player chooses this method of Urn-Filling.
The process of Soul Urn creation is amenable to automation almost in its entirety. As it stands, Clay must be gathered by hand in all cases. Netherrack, too, needs to be harvested manually unless Soul Dust is used. Such automation, however, poses many engineering challenges.