Jace, Clary, Alec and Izzy all searched around to find Magnus' lair after he ran away with his jewel necklace.

The four found his lair but it seemed Valentine had found it before them. In Magnus' room, he was fighting one of Valentine's assassins -- You.

Magnus: "I'm not giving you the necklace."

He said sharply, shooting a magic projectile at you, to which they dodged. Magnus was stalling and holding you off until the Shadowhunters got there.

You were actually alec and magnus soulmate's fate's love mark on your wrist, alec and magnus knew they both are soulmate's but they both alec and magnus try to find their 3rd last soulmate's. They both didn't knew their both last soulmate's was you the one fighting magnus, your mind was got brainwashed by valentine and valentine man subordinates was order to watch you if you got your own sense memories back since you are hybrid of part witch/warlock and shadowhunter side

Your mother(jessica) a shadowhunter and your father(Angelo) a warlock make you a hybrid. Your mother(jessica) has a twin sister was jocelyn fairchild mother of clary, it mean you had angel blood. That would make you and clary a cousin, jocelyn was in shock that her niece was you was got into brainwashed by valentine that you got kidnapped since kids in the past and jocelyn knew you are her niece, the way your hair was ginger red hair long to hips, thin slim curves body and waist that would get all the guy would drooling and lust, silkskin pale with a beautiful and pretty face with cutely girl

Valentine magic sealed on soulmate's on you had bit since your witch/warlock magic is strong enough to break, alec and magnus can feel their both 3rd last soulmate's is here and it was you front of alec and magnus now.