I think if Malcolm was a KotC, he was one of the one-shots. I proposed this theory before: Maggie is hiding out, working for Malcolm. She is found and attacked by creatures, either outsiders or denarians or both. The Knights show up, including the wielder of Amoracchius before Micheal. During the battle, Amoracchius is separated from it's wielder. Malcolm, being in love with Maggie, is able to take up the Sword.
Maggie, knowing the nature of the Sword, realizes that Malcolm truly loves her and falls in love with him. This could have burned out any influence over her, even from a shade of Lasciel. After, the Knights take Amoracchius and Malcolm and Maggie go back into hiding.