To foment a revolution against the ruling diarchy using a cadre of associates, coordinated via prophetic scrolls. Each of these associates is working on their disparate parts of the plan (some legal, some illicit) completely separate from one another, meaning the greater game is nigh impossible to detect. But since they're all working toward the same destiny as presented by the scrolls, their efforts are nonetheless in sync.
As for the BBEG himself, all this is a mere cover while he travels the land, tapping into the leylines of destiny in order to harness their power and impart it to every person in the world. Once that is done, and everyone can thus perceive theirs and others' places in the grand cosmic scheme, there will be no more deception, no more conflict, and as one, they will all work together in perfect harmony.