A common name for Mephisto's or Satan's realm. There are apparently several different hells, each ruled over bu a different lord - and all have used the title Satan at some point. The various lords of Hell include:
At some points, it has been claimed that at least some of these devils are merely aspects of one singular entity (see the Six-Fingered Hand story arc in the Defenders comic. At other times they are treated as separate, rival entities. Considering their deceitful nature, the real truth may never be known.