The entire series of Lost is the fateful prophecy & intervention of Jacob, in conflict with the simultaneous machinations of the MiB. Both sides, by very different Light & Dark routes, work towards the same endgame… their deaths and the end of the current cycle. The analogy of white & black in an eternal game is symbolic of these strategies. They can both see each others pieces, without knowing what the other was really planning.
The basis of this game evolved on the core of humanism by Jacob & MiB. Fundamental differences in their beliefs, and how it affected their view of humanity became the whole point of their game. Is man good but flawed, or civilized evil? What began as a simple board game became the hand of fate drawing select people to the mysterious Island, and a near-unstoppable force to test them. Their conflict is over with the closing of the final chapter… but life is conflict and the question remains.
The relationship between Jacob and the MIB was about conflict, about proving a point about humanity. Jack and the Losties won this argument. The over-riding message about humanity in Lost was a positive one. People have great capacity for good, for love, for collaborative living and community. It was their personalities, their lives, that ‘broke’ the Smoke Monster. Jacob’s prophecy finally proving that humanity has reached a point where it is ready for enlightenment. And not forced enlightenment, ultimately, through choice.
Light: Jacob needed Jack to fulfill his long & circuituous destiny… which included a number of pawns for him to lead, a love in Kate (later Juliet) to truly live & ultimately lose, he needed a foil in Locke (later Sawyer) to catalyze him, and so on. All of this is achieved by fateful nudges at critical times of Jack’s life (and others). His candidates are his most important pieces, and are protected as much as possible.
Jacob’s last prophecy: “They’re coming.” – This is in reference to Jack & his posse returning from their time travel to the Island ‘present’ by way of the Incident; the detonation of Jughead. Of course, they’re coming to kill the MiB in Jacob’s rebuttal to MiB’s ‘loophole’ and though MiB thinks he has won, Jacob has in fact been playing for a stalemate the whole time.
It may have also been the more direct reference to Widmore bringing Desmond to the Island. The final piece of the plan was needing Desmond (who has steeled himself against the ‘magic’ of the Island from Swan implosion) to remove the plug and turn off The Source, so Jack could kill the MiB and that the surviving 6 could leave. Ending the cycle.
Dark: MiB set up Locke to be leader by planting evidence and intervention, from current Island to needing time travel to implant a self-fulfilling prophecy to make Locke leader of the Others, and put him in a position to maneuver Ben to kill Jacob. This would allow him the freedom to plan the complicated demise of the candidates, freeing him from his Island prison. Whether he was bound strictly to the Island, or more likely confined to his role on the Island, is still unclear. Either way, the release he ultimately sought was the destruction of the Island entirely, his unbalanced attempt to end the cycle.
Smokey was pictured with Anubis (egyptian god of the dead) and was hinted as a ‘protector’ of sorts, while Dharma built elaborate defenses against him. Clearly he has been playing this game quite differently throughout the years, but always involving power struggles, manipulation, and a cunning intellect. Wheels within wheels. Testing candidates by scanning their memories and taking the shape of dead people from their past, especially ones they have a deep spiritual connection to, is one of his more effective moves. Smokey also seemed to enjoy appearing in various shapes, pitting one side against the other & turning allies against each other.
Ultimately, their plans have to merge for it to succeed, or at least they have to utilize the other’s methods. MiB’s long con allowed the cycle to progress, while Jacob’s prophecy allowed it to end.