Rappan Athuk: Level 5D (2018)

Level 5D: How Green Was My Dungeon
By Bill Webb & Tom Knauss

"However, as their deity’s influence waned and Tsathogga’s increased, their diminishing numbers could no longer fend off the influx of monstrous denizens and the Frog God’s crazed servants pouring into the region. Under Damarren’s guidance, his remaining forces retreated into the Dungeon of Graves itself..."