Due to it being completely below the surface, and to the massive amounts of kindling that would be required to completely illuminate the many, many tunnels, most, if not all of the lighting in the Lowlodge is magical in nature. Because of this, the city employs a host of various mages and conjurers to keep it consistantly lit.
The Lowlodge is kept secret to most, and news of its existence as a sanctuary is spread only through trusted word of mouth. Despite the precautions in keeping it hidden, including magical alarms and barriers around the various entrances (of which there are surprisingly few), its discovery by the denizens of Hell is imminent... and the citizens of the Lowlodge know it. Many of the refugees who live within its depths train daily in disciplines of violence, much to the displeasure of the kaba who were residents before them.