Duma is a fallen angel from the DC Vertigo series The Sandman. His name means "silence", and he is based on an angel from Jewish mythology.

Outside the Sandman mythos

In those tales, he is the angel of silence and death's stillness. According to the same stories, he is the guardian of Egypt and the prince of vindication. Based on this, one could assume that he was the angel who killed the firstborn Egyptians in Moses' time. At least one source names him a "Prince of Hell"; meaning that at some unknown point in time, he apparently displeased God and fell from grace.

The Zohar, a book of Jewish mysticism, describes his position in Hell as such that he had "tens of thousands of angels of destruction" under him, and that he was "chief of demons in Gehinnon [Hell; a more familiar spelling is "Gehenna"] with 12,000 myriads of attendants, all charged with the punishment of the souls of sinners."

Dumah is also the name given to the guardian of the 14th gate, through which the goddess Ishtar passed on her journey to the underworld in Babylonian mythology. Dumah may or may not be related to Duma.

Within Sandman

It is unknown how much of Duma's background from Jewish mythology that Neil Gaiman actually incorporated into the character. Many theories and interpretations have been put forward, but nothing is concrete.

In Season of Mists, we find that Lucifer has closed down Hell in frustration, handing off the key to the bemused Morpheus. Eventually, after much squabbling between various gods, God sends Duma and Remiel to watch over Hell. Remiel immediately rejects it. But Duma, being the angel of silence and thus unable to voice his protest, simply takes the key and puts it around his neck. It is thus that Remiel and Duma become the guardians of the Sandman mythos' Hell.

Duma's sacrifice in taking the key enlightened Remiel, who subsequently accepted the heavy burden of rehabilitating lost souls.