Found on eBay:
Steve Ditko, art. "I Dared to Defy Merlin's . . . Black Magic!" Chamber of Darkness 6/2 (Magazine Mgt. Co. for Marvel Comics Group, Aug. 1970). No writer credited.
A man is on vacation in the Balkans and visits an antique shop, where he comes across Merlin's diary (see also the Gargoyles episode "A Lighthouse in the Sea of Time"). The man does not believe in magic. The shop owner warns the man not to touch the book, but he does anyway and is transported back in time to Camelot. There, he meets Merlin (looks like Merlin I) who casts a spell on him. The man is then returned to the present by Merlin, and he discovers that Merlin has made his hair turn white. Convinced magic works, the man leaves. It is then revealed that Merlin is the shop owner.
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