The Mothers are immortal, like Mab she couldn’t be killed even with iron. Only the Stone Table which appears to have been set up as part of the Mantles, a deliberate backdoor, could kill them, or on Halloween when all immortals are vulnerable.
Many deities have cropped up under various names, the Fates could easily also have been Baba Yaga and her sisters, and the Norns etc. Lots of powerful triumvirates of witches. You have the original trio of the maiden, mother and the crone, they put their power in one set of Mantles, and additional power is added by other deities on Halloween to power them up, most notably the Crone, and a lesser extent the Mother. At the same time the same applies to Summer, a different triumvirate and the Stone Table is created regulating the Mantles and setting the limits upon their use, creating a balance. Some of the ordinal donors of power stay on under the new Mantles. All this is done under the strictures of the White God, be in the mortal world under lesser power, or face exile to the Never Never.
The knights are created at this time as well, the Mantles most in the real world, again from donated power. With the Courts created, the Fae (all Wildfae at this point) start declaring for their Court.