Marguerite is a French Canadian Vampire who first appears in the Darkest Powers/Darkness Rising short story Kat. She was a former employee of The Edison Group and part of the network who monitored the Group's experiments. She stole their subject Katiana from them when she saw how miserable the girl was and was still expected to only observe her. She now serves as Kat's guardian, watching over her and moving them frequently to try and make sure the Edison Group doesn't recapture her.

She is described by Kat as having a soft French accent and being beautiful, small with a heart shaped face, blue eyes and blond curls. She has been a Vampire for over a hundred years, growing up in the nineteenth century and physically looking twenty years old.

In the short story Kat she is the titular characters guardian, keeping her on the run from The Edison Group who finally catch them and 'accidentally' kill Kat. After Kat is reborn as a Vampire they go back on the run. Six months later during the events of Hunting Kat she rescues Kat and Neil Waller after they are targeted by bounty hunters seeking to sell them to The Edison Group.