Shadow, that sounds _awesome_. A few thoughts:
1) is it possible for the cave-in to completely block the path to town?
- if so, can the player port back?
- if the player ports back, can they get back to the blocked-off area?
2) what do you think of map features that "jam" portal spells, to make getting stuck even worse? (it could mean time to start a new town)
3) can the enemies intentionally try to start caveins to harm the player or block them in or out?
4) if you do some of the meta-game stuff we talked about earlier, could a group of "goons that hate the player and have tracked him down to this part of the world" lay in wait and try to cave-in the player when he least expects it?