A grief seed (グリーフシード Guriifu shiido?) is the item from which witches are born. Usually, defeated witches drop grief seeds. This will not occur with familiars.

Magical girls need grief seeds in order to cleanse their soul gem. Grief seeds will become visible to magical girls, as well as the labyrinth when they are almost ready to hatch.

A soul gem can become a grief seed when magic is used too carelessly, or when a magical girl forgets to cleanse it.