Mab, was the youngest of the three Legendary Fae Queens, alongside Maeve and Mora. After her death it was presumed she was proclaimed a goddess: known as Deanna. Whether or not this is true is unknown. She is the founding ancestor of House Ashryver of Wendlyn, and her descendants have inherited their magical powers after her.
It was stated in Heir of Fire states she had fair hair.
Mab had been the youngest of the three Legendary Fae Queens. Some time in her life, she fell in love with a human prince. Mora, who is her older sister, fell in love with a mortal as well. Naturally, Maeve disapproved of their actions, and it has been stated that both sisters gave up their immortality to live shorter lifespans with their mates while simultaneously evading Maeve's wrath. Some presume that the two Fae Queens were loved fiercely by their human mates, and so they became mortal too, having tied their fates with their mates.
After her death, Mab was presumed to be proclaimed as a goddess, known as Deanna.
Whether or not she merged with the original Goddess of the Moon, or replaced her, is unknown.
Empire of Storms
It was mentioned by Maeve, that her bloodline ran true, so that all her descendants who inherited her shifting abilities would gain her immortality upon Settling, as well. This is not the case with her Water Magic alone, since Evalin did not go through the Settling, and was not immortal.
Before sacrificing her immortality to live with her human prince (possibly her mate), Mab was a full-blooded Fae, with all the standard abilities of the Fae.
Secondary animal form - White Swan.
Magic - Water Magic. It was mentioned that House Ashryver inherited their magical powers from Mab. Since Aelin's mother was shown to have water magic, Mab is assumed to be a full water-wielder.
Alongside her standard water abilities, she is also immensely affiliated with her element. This is her "Water Affinity", reminding the bearer of their salvation, and their self-preservation. Even a drop her magic grants the user healing abilities (Aelin). Since Mab had the full powers of her Water Magic, she would have had immense healing abilities.
 - Sarah J Maas's Pintrest board - pin of Mab <https://au.pinterest.com/pin/246853623301794045/>