There's a great source of lonely fun out there that, like traditional sources of lonely fun (i.e. preparing a dungeon for play), will enable yet more gaming in its wake:
Here's a rundown of what happened in my 2nd game, in which I finally realized how adventurers work.
The dwarves of Enog Rinmol made it a few turns, carving out a small but sturdy little settlement under the earth and making money with a gold mine (literally). Sadly, they struck a cavern containing a deadly microbe, some kind of plague, and wiped them all out immediately. Sigh. That happened in my first game, too.
Anyway, a magma pipe formed deep, deep down, sending up a volcano (and thus an awesome, convenient ingress to the dungeon once it cooled).
Humans settled the nearby Overworld, their farmlands soon quilting the nearby countryside. A tribe of fungaliths (??) showed up in higher caverns, and began exploring nearby tunnels, only to encounter a human city, wipe it out, and die off in the process.
A settlement of earth-men (?) claimed new chambers hollowed out in the side of the now-dormant magma pipe, just off the dead dwarves' gold vein. They fought off numerous incursions from green slimes, wandering evil wizards, and other critters, managing to stay strong enough to hold off an encroaching dragon from the deep.
Giant ants actually drove the dragon from its lair, to my surprise. They showed up in the old dwarf-hold, and kept it at bay until adventurers could show up and wipe *them* out. Eventually, for want of monsters in the dungeon, some undead warriors appeared in a cavern off an underground river. They were soon cannibalized by a vampire who floated in off of said river (a custom monster! Shyeah!), who was in turn wiped out when the Thought Lords (psychic slave-masters) showed up.
Here's where things stand: a crew of adventurers, battle-scarred but staggering under their pile of loot, is encamped at the foot of the dead volcano. The fungalith caverns stand empty, whatever strange things they called wealth sitting right where they left them.
The earth-men are weakened, but wealthy. Again, I have to wonder what they would consider treasure.
I forgot to mention the kobolds - they settled into the tomb where the undead warriors dwelt, and now hold their treasures as their own. The Thought Lords are hiding out within the depths of their vaults, having taken heavy losses from the vampire.
The dwarf-hold stands utterly empty, though little of the gold vein has been tapped.