A Builder is a specialized unit which serves no function in battle but remains invaluable in a war campaign. They can be used to build shipyards, roads, towers, and even repair razed cities. They cost more, not only for the construction of the unit, but because the Builder's Guild must recruit and train a crew of able Engineers to work the Builder. With the capacity to construct structures that produce merchandise, the unit quickly pays for itself.
Engineers, while trainable in all races, are considered a breed of their own. They serve willfully, content to spend their pay on trinkets, Dwarven puzzle boxes, and on new tools. They have little regard for lodging or personal hygiene and delight in the chance to "work" (play) with the Builder, safely away from any chance of getting killed.