The Easy Exploit Compendium

[Flame of Anor]

Not the only problem. NOT AT ALL.

After you've done this once or twice, the goblins get wise to it, and start XP farming each other. The next time you come back, you get blasted with a Fireball, a Flame Strike, a Baelful Polymorph, a Dominate Person, a Stone to Flesh, and a Dimensional Anchor from six casters of your level from the population you've been oppressing. And then the ubercharger melee brutes have at you.

And you'd deserve it, because keeping an imprisoned population of sentient beings to kill for your amusement would be an incredibly evil thing to do.