Simon Magus, Ebekanezer [ the biblical one], Soloman, Nikola Tesla, Khufu, Aleister Crowley, Hermes Trimegistus, Faustus, Nicolas Flamel, St Germain, or just makeing one up from the dark ages.
personally id go with soloman, arguably as powerful as Merlin and with the more judeo-christian slant you could possibly incorporate something like soulfire into it.
also read changes.
its good, and has vital info youl need to know for your concept.
Brian Blacknight