Lailah is the Jewish angel of conception. According to the book "Before You Were Born," she was the angel that brings souls and the seed together and then sees to it that the seed is planted in the womb. In doing so, Lailah serves as a midwife of souls. While the infants grow in the womb, Lailah places a lit candle at the head of the unborn infant, so they can see from one end of the world to the other. She also teaches the unborn child the entire Torah, as well the history of her soul. Then, when the time comes for the child to be born, the angel extinguises the light in the womb and brings the child into the world. And the instant the child emerges, the angel lightly strikes its finger on the child's lip, as if to say "Shh" and this causes the child to forget everything learned in the womb. It's implied that the knowledge is still there, but merely forgotten.
Lilith is often compared to Lailah as an evil opposite, seeking to kill newborn children while Lailah seeks to protect them. Both are also related to the night. She is ranked as a Dominion.
"An angel in Judeo-Christian lore that presides over conception. She is the intermediary between pregnant women and God. When a woman conceives a child, the seed is given to God, who then decides the child's sex, appearance, and destiny. After such things are decided, a new soul is placed into the woman's womb."
Unlike most Heralds, Lailah does not look as angelic as the other angels, sporting a pair of black wings a face covered by an ever-smiling mask, a mourning hat and her body is fully covered by a black mantle.
Lailah not being unique despite being a named angel can be explained in her role in the myth where she has to aid all of the unborn children, which would be physically impossible even in ancient times.