The Demon Crypts are the location where Na-Krul himself was summoned into Sanctuary. Polished black marble textures decorate this place of evil beauty. Demonic hieroglyphics and strange devices are carved into the walls and floor, and spiral columns support the ceiling. Lava runs under the floor, covered with grates. There is an orange underglow reflected off of the shiny marble surfaces. Tombs and statues are everywhere. This is the home of the demon nobility, and is populated with the dead, the decayed, and, of course, a myriad of demons. The barrels that appeared throughout the original game are replaced in the Demon Crypt levels with suitably gothic urns. The level is very difficult, with many monsters crawling in its depths.
As you descend deeper into the Demon Crypt levels, the halls become progressively more crumbled and ruined as the source of the lava is approached. Finally, at the bottom level, you will encounter Na-Krul himself. Far more powerful than the other inhabitants of the game, Na-Krul can be weakened by using the hints contained in the Reconstructed Note to read the spell books found outside Na-Krul's realm.