ArchfiendBobbie
First Post
I'm confused by the people that say it can't be done. I get there's questions about whether it should be done, but that's a different question. In addition, as I said before, you'd be surprised by the number of people that would "rather die than surrender".
While it would be difficult to stop a high level group, it's not impossible. Simply throw more monsters. Throw multiple Tarrasques appearing in waves if you have to. To knock the PCs out instead of killing make sure that the last spell cast is not damaging, hit them with melee and knock them out or keep doing relatively small amounts of damage and have some NPCs casting Sleep spells ever other turn. Eventually it will work.
You do have to stop teleportation and other means of escape, something as simple as a Hallow spell will do that (be ready to counterspell depending on how you run it).
At a certain point it does break the unspoken rule of D&D that encounters should be "fair" in that the PCs should always have an option to win, or at least to escape to fight another day. Breaking that unspoken rule may upset some players.
It's not that it can't be done. It's that it's so monstrously difficult to do with the rules as written that you have to effectively pray the players go along with it. If they don't (and many won't) then your options can be easily limited to either beating them into submission and hoping they don't die or escape, or using GM fiat to railroad them.
Even for DnD, 5E is extremely bad for subduing people. Many other gaming systems, and even other editions of DnD, do it better.