So I been on a forgotten realms reading kick again and got an idea. This would probably be for the far future, but I think its pretty neat and would encourage larger parties of players.
This would be something used once you have gotten into a REALLY difficult and far-away area with a larger party. Having the ability to craft a mini mythal of sorts. It would require multiple casters (probably of several varieties) and they would all have to be of a set minimum level. The casting would take a fair amt of time and during it the casters would be unable to attack/defend. This casting would also increase the spawn of monsters around it and the other party members would have to defend them. The result would be a safe zone out in that area. No monsters would spawn inside it and they wouldn't like to come near it. Within it you could even open a portal or something. There is a lot more you could probably add on to something like this, but thats all I can come up with off the top of my head right now.