Complex sentence: In legend, a cauldron is usually where leprechauns keep their treasure, and also where witches prepare their potions, most notably the weird sisters in the play Macbeth.
Split into simpler sentences: In legend, a cauldron is purported to be where leprechauns keep their treasure. Traditionally, or in myth, a cauldron was also used by witches to prepare their potions, most notably the weird sisters in the play Macbeth.