In retrospect you feel that crossing your master, the High Necromancer himself, may have been a bad idea. Now you're locked up in an explosion-proof dungeon with other wretched goblins, and you know you're in for a world of suffering.
The penal servitude consists of getting hands-on knowledge of explosive contraptions crafted by the High Necromancer's enemies. You have to find out what sets them off and what kind of damage they can do, making it possible for your master to craft contraptions of his own. Your tools are a bag of sneaky tricks and unlimited, although painful, resurrections.
The only things you've got going for you are the measly bucks you can earn by doing the High Necromancer's bidding, and the greed of your troll jailers. Hopefully you can bribe your way out of this miserable existence before the job costs you an arm and a leg.