Complex sentence: The Rings gave power to the bearers, but where in secret designed to enslave the Bearer to a Master Ring: the One Ring which Sauron himself forged in the fires of Orodruin, the Mount Doom.
Split into simpler sentences: The Rings gave power to the bearers, but where in secret designed to enslave the Bearer to a Master Ring. The One Ring which Sauron himself forged in the fires of Orodruin, the Mount Doom.