a mixture of unpleasant or dangerous things

The smog is composed of a witches' brew of car exhaust and smoke from factories. 雾霾是汽车尾气和工厂废气的混合物。

a situation that has many different parts that are difficult and dangerous

The country is in turmoil, a witches' brew of poverty and warfare. 这个国家处于一片混乱之中，充斥着贫困与战乱。