Instance Gems & Rooms

This is a basic framework for a class of temporary rooms with modifiable
stats.  Instance Gems create Instance Rooms, which may be different
areas with different monsters, treasure, and experience gain. Currently,
the rooms boot everyone after one minute and expire. That's just a test
duration; I expect them to last at least a couple minutes in practice.

When you use the gem, you're teleported to that room. Right now, the
basic example room is a random room, spawning a random mob, with random values
for treasure and experience gain between 100% and 500%.

There are many ways we could use this, and I'm hoping for some feedback
before I proceed further.

We could have Instance Gems drop in a widespread manner, using them
to give builders 'something different' for a couple minutes - and with
increased experience gains, giving them a sort of 'quick rush' feeling.

We could have Instance Gems expire after a short time, so they're
limited solely to builders. Or they could last until used, so that 
players can hoard and trade them.

We could have Instance Gems given as rewards for quests.

We could make Instance Rooms that last longer, and use them as
boss lairs.

What do you think?