[url=http://en.wikipedia.org/wiki/Godfather_Death]Godfather Death[/url] - how mister Death treats his godchildren
[url=http://www.oldrussia.net/vas.html]Vasilisa the Beautiful[/url] - the original fairytale
I searched up black horseman...found a page on the four horsemen of the apocalypse. I'm not doing that, rest assured!
(though, it would make sence, since the order is white, red, black, then the pale horse of death...which wasn't intentional when I thought that...though, OMG, I think that might be what was originally implied in Vasilisa the Beautiful! Since Vasilisa asks Baba Yaga each about their names, then the last thing she may have inquired about would have been her death...)
The riders/horsemen are implicitly knights, as well as personifications. So, white knight, red knight, and black knight.
I'm RPing as the Night, and NPCing the other two.