A cauldron was a metal vessel using for boiling liquids in.
The Clocksmith threatened to drop Apolena in a cauldron of molten lead. (AUDIO: The Eighth Piece)
The three Carrionites Lilith, Bloodtide, and Doomfinger, who inhabited All Hallows Street in 1599 London, kept a cauldron in their home for their witchcraft, including remote viewing. (TV: The Shakespeare Code)