witches' brew vs assortment

witches' brew and assortment both are nouns.

Word	Noun	Adjective	Verb	Adverb
witches' brew	Yes	No	No	No
assortment	Yes	No	No	No

As nouns, assortment is a hypernym of witches' brew; that is, assortment is a word with a broader meaning than witches' brew:

Other hypernyms of witches' brew include miscellanea, miscellany, mixed bag, mixture, motley, potpourri, salmagundi, smorgasbord, variety.

witches' brew (noun)	assortment (noun)
a fearsome mixture	the act of distributing things into classes or categories of the same type
	a collection containing a variety of sorts of things