I haven't had the first encounter with my players yet, but I have this long-con side plot going on. It involves a puzzle map that leads to a series of dungeons which leads to an "ultimate treasure". That treasure is the language of creation. In the end, the players might trigger the re-release of the spellweavers (which I'm flavoring as a race interested in ascension to godhood and world domination).

This plot is being run in a west marches, so I'm banking on the hive mind for creative explanations on why someone would set up these series of puzzles.

As an addition to this side plot, I decided that the original race that discovered the language of creation was trapped in a pocket dimension as punishment by the gods because the language of creation is solely reserved for gods. BUT not all of the spellweavers were punished. There was a faction that did not believe in pursuing the language or ascending to godhood and was spared by the gods. All of this happened thousands of years ago, so the species has evolved into a race of giant nonmagical sentient spiders. These spiders have a very skewed view of their ancient history, but players might be able to get more clues here.

Gosh I hope my crazy rambling makes sense.