Papa Midnite is coming to Constantine next week, and fans of the comics are sure to be excited by that.
A number of viewers of the TV series, though, probably saw that and were wondering what was going on.
In the comics, Papa Midnite is an immortal mob boss, businessman and voodoo practitioner. He is an uneasy ally and sometimes an enemy of John Constantine. He served a similar role in the 2005 film Constantine.
He first appeared in Hellblazer #1 and was a key part of many of Constantine's early adventures. He was also apparently slated to appear in the pilot episode, but was cut late in the game; a script that leaked online reportedly featured the character in a cameo.
Midnite is a master of voodoo; he's able to create and control voodoo zombies, alter his physical appearance at will and a number of other handy skills in addition to having a similar level of control over general magic to Constantine's.
Born in the 18th Century, Midnite was a dabbler in the dark arts back then and when a would-be slave rebellion recruited him to make them a protective spell, his failure led to his sister's death. He was cursed to immortality at the same time, at least as long as whites remained dominant over people of color in the U.S.
He's been using his sister's decapitated skull to speak with the dead ever since, and has been very active as one of the world's most powerful mystics since the 1980s or so.