Being a delving group, Antlings were slow to expand, but they nevertheless explored most of the abandoned halls. They had so far avoided close contact with the diseased waters of the river; a lone goblin far downstream was not so lucky and became possessed by mutagenic slime parasite. Transformed into a deadly creature known as Iggithushalo, "The Misshapen", he (or rather it) began to stalk the few still surviving Tritons.
The miners explored all of the upper tunnels, growing restless in their search for gold that they knew was there but which still eluded them. At the same time, it had not escaped their attention that the local climate and soil were unlike anything seen in this valley a mere ten years ago. With the next caravan, news traveled back to the nearby kingdom of Bok-Anlar, and by the summer of 63 an army was assembled to claim these lands.
The campaign met with moderate success. Anlaran knights stormed the outlying Theliiri villages but could not assert their position any further; they built a border guard about three spans from the battle site, contenting themselves with the lands west of it. For now.
The Theliiri set up hidden scout posts to watch the humans, and organized another expedition into the depths, as they wished to ensure they were not being threatened from below. The mushroom caves were now connected to the underworld, and parts of lost dwarven treasures were recovered. Emboldened by their success, the beast-elves built a new forest-town to the northeast, giving it the name Lenearíle after flocks of seabirds often seen in the skies above it.
Iggithushalo moved its lair east, preying on the Tritons and devouring everything else in its path until nothing was left. The Antlings and the humans kept exploring.
***
Far away, in another city, two dwarves were repeating a conversation that had happened many times.
"Ah can't believe ye sold da map to dat human, Urist! It be yer father's heirloom!"
"Oh, don't be so dramatic, Uncle. Mapmaking is my business now, if you haven't realized. I made a few copies of that map, and they are for sale."
"But what of our return? Yer giving us up? Yer wanna humans take Asteshdatan, is dat what ye'd like, Urist?"
"..."
"Blast, yer serious. A'right, figurin' we do without ye."
"Uncle, we have waited seventeen years. We can wait till the next spring. I promised I'd contribute and I will."
The dwarves will return next year to reclaim what's left of their ruins. But they will not be without competition; in fact, as the spring of 64 arrives on the calendar, there is a troglodyte horde building their warrens along the dry riverbed and also a great beast in the abandoned mines: a dragon!
Make a choice whether the dragon will be Lawful, Chaotic, or Hungry. Lawful/Chaotic dragons will demand tribute from groups and may give out quests to adventurers of matching alignment, whereas Hungry dragons will just try to kill everything and take the treasure.