(I'm going to try quoting this time in case the forums don't notify you without the quote)This is a hard nope from me, and you might get some static online-- but I don't see anything wrong with it as a setting you and publish and play in.
This is an idea for a Campaign Setting I had, but I want to make sure it doesn't give people bad vibes before presenting it to the players like this.
The PCs are refugees from the various Realms they come from, which were subjugated by the Overlord. They are rescued to take refuge in a giant bazaar city called Lakk_Szatz'i (The Well of Worlds), which rests in the center of an unending but hidden desert Realm. Here they take an oath to become indentured Treasure Hunters to begin a new life.
Also a reminder that the assumption behind the setting is that these refugees agreed to take these Oaths in order to be allowed to operate in The Well, but it's of course true to say they didn't have much choice because their home Realm was being subjugated by the Overlord.
So, basically, they were coerced, under duress.
A couple of questions:
1) How does anyone know the oath is broken? "I'm sorry, boss, but the whole thing was a bust. We barely made it out alive, and all we got were these lousy T-shirts..."
2) What happens if the oath is broken? Do loops of shadow envelop them wherever they are, and swallow them up transporting them into a dungeon that competes with the Nine Hells? Does the boss then have the right to send a bunch of thugs of questionable quality to put a squeeze on the PCs?
maybe have the first session be their first arrival at the Well where they are offered the Deal by their Patron to take the Oaths in return for protection and the right to trade there way out of their Life-debt.
The only question then is what happens if
1. they chose not to take the oaths
2. They break their oaths
3. They choose to go back to their own realm

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.