Some of my personal philosophy, when it comes to how to enforce rules, is I think that there needs to be some questions asked:
These questions include:
How Frequent is the Rule Break?*
How Harmful is the Rule Break?
How Easy is the Rule Break to catch by the DM Team? How possible is it to reinforce?
What will we loose by mechanical enforcement of the Rule Break?
The last one of these to me is the most interesting. Because roleplay is rarely black-and-white and a lot of the time, for every 10 examples when something is done poorly, there's 1 example when it's done well. And especially if we put mechanical limitations in place, we DO stop that 1 example.
Lets try and break down this sitaution
How Frequent is this Situation? (Slaves going back to the underdark even after being freed?)
I honestly don't know. I don't have numbers on this, and I don't think the team has been hugely monitoring it. Maybe we should? I'd say it's not entirely uncommon, but it's not hugely common either.
How Harmful is this Situation?
Althought I agree that this isn't an ideal sitaution, I'd personally also argue that It's not neccesarly the a massive issue. It's frustrating to some and irritating, but I don't think that it's causing players to leave in droves, or creating a hugely imbalenced issue mechanically. Does that mean it's not worth adressing?... Not neccesarly. But if we're being honest I also dont' think it's The Worst Thing Ever.
How Easy is The Situation to catch by the DM Team? How possible to Reniforce?
Well, it's possible certainly, if we all keep a weather eye on things. But let's be honest, we arn't always that great at that, and it's not the sort of thing that easily shows up in a quick log search. If we have the team willing to be very attentive to it, we could catch it. But honestly we have a lot on our plate, so we have to be wary about adding more. This is hte sort of thing that we sould need people to report, which people have, and do.
What Will We Loose by Mechanical Enforcement of the Situation?
This sort of storyline is long and complex, and i think heavy reinforcement would be a mistake. Because it SHOULD be viable for slaves to remain in the underdark, after being freed. My main concern really, is that some people are using the mechanic as a way to 'get trust' in the UD, and get all the advantages of being an Outcast (portal access, Undercommon, friend connection) whilst avoiding the dreaded outcast 'Tag.' I feel this blurrs the lines too much, and I think some sort of mechanical reinforcement to prevent that isn't a bad idea.
That said, I also don't think ti's That Big a Deal. It isn't perfect, and it is deserving of a fix, but at the same time it's mostly a 'poor roleplay' situaiton that can mostly be ignored. Again- not advocating AGAINST my idea, but I also don't think it's the most urgent issue in the world.
- Rule break/setting break/poor rp ect. We'll say 'rule break' for ease, even though what we're talking about isn't strictly that.
I'll also note Re. Vespidae's points:
The thing about playing a slave is a) You often have something to do. b) You often have a neat, built in 'goal' of getting free. C) You have a lot of pcs often pushing for or against that goal, which can make a really neat, intence narrative.
The problem when playing that from the start though, is that you need a narrative or something AFTER that. This is an issue that's on the shoulders of not just the slave pc, (though a lot of it is!) but also on the person/people that work to free them.
So what you get is
Chainbreaker: GET FREE! YOU NEED TO GET FREE!
Slave: OK! Thanks to your help I'm free!
Chainbreaker: YAAAAY! I WIIIN I WIIIIN I WIIIIN I FREED A SLAVE I'M THE BEST YES YES YES YES! I WIIIIIIN!!!!
Ex-Slave: Yay! Ok uh, what do I do now? I've no direction in my life. I've left all the people I spent time with. I'm alone here and-'
Chainbreaker: Yeah, yeah, whatever. The point is I WIN! you do.. IDK, whatever. I don't care, I've got my win.
Ex-Slave: .... .... Well um. this is dull. I'm going back down.
Chainbreaker: WHAT? NOOOOOO!
Now to be clear I am absolutly NOT accusing anyone in this thread of the above AT ALL! A chunk of the responsiblity in the above is also on the first player to work out what they're going to DO upon becoming free. Most of the responsiblity even. But I do think a level of thought should be given by chainbreakers that this isn't always the end of the narrative.
This too shall pass.
(I now have a DM Discord (I hope) It's DM GrumpyCat#7185 but please keep in mind I'm very busy IRL so I can't promise how quick I'll get back to you.)