From the back cover:
The bulk of the City of Penance is a madly stacked and sprawling ruin, only superficially explored by the relentless rafters and treasure-seekers of the surface world. Every home in the city has a hundred others lost beneath it, and every city street stands atop an incredible three-dimensional maze of corridors, alleyways, and crawlspaces--a maze where time has left nothing unchanged, eroding and distorting the framework of magic and even the laws of physics themselves.
Within Wrack & Ruin you'll find:
- 3 new player character races
- 5 new prestige races
- 2 new prestige classes
- New magic items, monsters, and spells