Chernobog

[TerminallyUnique]

I found a reference in the latest issue of Fortean Times which makes mention of Chernobog, whom 'in Ukranian tradition, was a chthonian Lord of Death, described as "a black sun beneath the earth".'
Apart from the fabulous description, does anyone else know of such a person/being from history?
Perhaps someone might have some references I could look up?
Ta.