There doesn't seem to be a singular source, like say, Norse mythology. I've always been flummoxed by the random mish-mash of creatures and influences from which the series draws its influences. But Mortal Kombat Shaolin Monks works on a number of levels, some of which are obvious, and some seem to be almost by mistake.
Numerous other developers have tried and failed. That is to successfully shift a fighting game into another genre. Aesthetics Ed Boon and his talented development team have done something that seems so natural and seemingly obvious that one wonders why it wasn't done before. Shaolin Monks is a pretty basic action-adventure title, but because the fighting move list is so deep and the action so fun, the result produces an arcade-style joy like few other games have. Finally breaking free from the confines of the fighting genre, Midway's Shaolin Monks brings the fighting army of Kombatants into a different setting, yet retains the fighting moves, styles, personalities and Kombat lore that have made the franchise such a strange cultural phenomenon.