|“||And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a Mark upon Cain, lest any finding him should kill him.||”|
The Mark of Cain, sometimes referred to as the Mark of the Wanderer, is an ancient protection mark meant to protect the bearer from anyone with the intent to harm them.
Anyone who attempts to hurt a person bearing the Mark will be punished sevenfold. When not triggered, the Mark remains invisible on the wearer's skin, but when he/she is attacked, the Mark will glow white and the assailant is struck by an invisible force with power equal to the force that was to be used on the bearer. When someone comes at the bearer with a death blow, the attacker would be reduced to salt. While the wearer is invulnerable to attacks from others, he/she can still be hurt by oneself or by accident.
The origins of the Mark are rooted in the Biblical story of the brothers Cain and Abel; as punishment for murdering his brother, Cain was bestowed with a mark that protected him from all harm but also prevented him from ever dying, thereby condemning him to an eternity of wandering the Earth burdened by his sin. A divergence from the established beliefs about the Mark among mundanes and the Shadow World is that the former believe that the Mark was bestowed by God as a curse, while the latter—specifically from sources gathered by the Praetor Lupus—say that ancient Seelies gave Cain the mark.
In 2016, the Seelie Queen, in an effort to protect the Daylighter Simon Lewis, bound Simon to a deal with her. The Queen had her followers forcefully place the Mark on the unwilling Daylighter, who did not know what the Mark entailed and had to figure it out on his own after the Mark reacted to an attack for the first time.
When two of Lilith's disciples fell victim to Simon's Mark, she worried and acknowledged that it could ruin her plans if he even attempted to stop her. And indeed, when Simon provoked Lilith into attacking him, the Greater Demon exploded and was banished back to Edom.
- In the books, the Mark of Cain is a heavenly rune and is considered the first Mark a human ever received from heaven. The Mark was and should typically only be given by God, though Clary was able to draw it on Simon due to her gifts.