The inscription that Dud sees on the Lynx ring (and tries to pronounce) is "Superius Sicut Inferius", conventionally translated as "As Above, So Below"-- which is the title of the episode. The English phrase doesn't come up anywhere in the episode itself. "Superius Sicut Inferius" is a phrase from medieval alchemy, from The Emerald Tablet of Hermes Trismegistus, which says, in full: "Quod est inferius est sicut quod est superius, et quod est superius est sicut quod est inferius, ad perpetranda miracula rei unius"-- variously translated: "What is lower is like what is higher, and what is higher is like what is lower, to work miracles of the one thing."