Sizemore Rockwell is a Dirtamancer in the service of Lord Stanley. His main duty as the story opens is to animate crap golems. Earlier, he bored a large number of mining tunnels in the volcanic base of Gobwin Knob; however the gems have now been mined out. He had also, at some point, crafted multiple Soft Rock Golems, Hard Rock Golems, Acid Rock Golems, and one Metal Golem.
His personality is that of a meek intellectual. He has attempted to learn various types of magic, and has a basic theoretical understanding of magic in general, but has no practical ability at using any magics other than Dirtamancy.
Soon after Parson is summoned, Sizemore teaches him some of the basics of the Erfworld magic system, and teaches him about several magic items, and about the Thinkamancy link. After Stanley leaves Gobwin Knob, Parson leaves him to modify the tunnels under Gobwin Knob along with his golems.
Real World References
It is also worth noting that one of the earliest patents for a shovel design was given to James B. Sizemore.