The Order of Merlin
The Order of Merlin is ostensibly the very same wizard order to which its titular head belonged. He himself is thought to have been a follower of a much older tradition, now lost to time, and the ravages of the Inquisition. Now, it bears his name, and his purpose.
Practitioners of the order believe they are meant to guard the realm of Albion (an earlier name for England) and its True King, until such time as the throne is restored. Not only, they claim, is the True King the rightful lord of England, but he was also meant to usher in a new era of enlightenment. His failure, due to treachery from within and without, indirectly allowed the Dark Ages to occur. Though they have now ended, the Order maintains a greater calamity awaits, and mankind is doomed without the True King's guidance. No longer does his mandate extend merely to England, but to the whole world.
Once, the crown of England employed wizards, diviners, and sages of all kind. Though they became scarce as Christianity took root, they never quite vanished--that is, not until the death of Elizabeth I of England, when the Catholic James I expunged all trace of England's pagan past. Until that time, members of the Order guided the British monarchs; since then, they have taken refuge in the New World, and expect the True King to emerge there.