Let us presume that the Locke we see resurrected in season 5 is in fact that "Man in Black" that was talking to Jacob at the beginning of "The Incident."
If this is the case, then why does he seem to NEED Richard to lead him to Jacob? At the beginning of "The Incident," the MIB visits Jacob near that same statue. Why did "Flocke" seem so dismissive about the foot when Richard brought him there? He seemed genuinely startled at the revelation that Jacob would be there.
Which brings me to a theory; Jacob and the MIB are both affected by some kind of perception filter that prevents them from being able to intrude upon each other's "home." Jacob can't perceive the MIB's "temple" and the MIB can't perceive Jacob's statue. But... those places are also the only places where Jacob or the MIB can actually be harmed. That's the loophole. The MIB needed someone else, someone trusted by Jacob, to "show him" Jacob's statue. By himself, the MIB could stare straight at the statue and see nothing that would grab his attention. Both Jacob's pawns and the MIBs pawns can travel to either location unescorted. This is all part of "the rules."
In this way, the "game" that is being played more closely resembled the game of "Nim" then either chess or backgammon. Nim itself is an ancient game, one that is deeply rooted in mathematics and allows both players to use the same pieces. Nim is a "poverty game" in that it is actually played to loose. That is, the winner is the one who loses according to the normal game rules. Such games generally have rulesets that normally encourage players to win; for example, most variations of checkers require players to make a capture move if it is available; thus, in the misère variation, players can force their opponents to take a large number of checkers through intentionally "poor" play.