Fall to the Forest: Dungeons of Underhill by Deacon Frost

When the world of the Faeries began to collapse, they sought refuge in the only place they could. That salvation lay in the hope of resurrection and rebirth. The Ancient One spread the souls of the Faerie across the Universe, placing them as seeds that would grow into mighty Dungeons, each a potential location for their people to be renewed.

No one on Earth was prepared for Dungeons to start popping up and causing technology to degrade. It was something they were going to have to adjust too, because Earth would never be the same.

Contains some adult content, violence and language. Also present: Fae strangeness, unconventional lifestyles and exploding mushrooms.