Witches

Spoiler Warning!!!

A Witch is a term for creatures born after a Magical Girl falls into despair, uses too much magic without purifying her Soul Gem with a Grief Seed, or a Familiar kills about 5-6 people, a Witch is born. When Magical Girls become Witches, their Soul Gem turns into a Grief Seed as a result. Witches hide in mazes called [https://wiki.puella-magi.net/Madoka_Magica_Trivia#:~:text=The%20labyrinths%20consist%20both%20of,of%20the%20magical%20girl's%20heart. Labyrinths] and control minions called Familiars. They are very dangerous to humans, hence why Magical Girls fight them. And the cycle repeats once that Magical Girl becomes a Witch, trying to killing one person for each one she saved. After Madoka Kaname recreates the universe however, they are erased from existence completely and have been replaced by Wraiths.