Complex sentence: Inside, after being initially rejected, they are permitted to see the Wizard (appearing to them in the form of a large head surrounded by fire), who agrees to grant their wishes when they bring him the Witch of the West's broomstick.
Split into simpler sentences: Inside, after being initially rejected, they are permitted to see the Wizard (who appears as a large head surrounded by fire). He agrees to grant their wishes when they bring him the Witch of the West's broomstick.