Artorias could feel the Abyss struggle against the Dragonborn's magic. It seemed to grab onto him all the more. The Knight was brave and his will was strong. He did all he could to endure, not just for his own sake for but Sif. He didn't want to alarm or worry the wolf, after all. He clenched his teeth and closed his eyes, bowing his head as he did all he could to resist the Abbys becoming stronger within him. He could feel it being drawn from him.
Sif growled at the darkness as it came from Artorias, drawn into the soul gems. The wolf watched, ready to strike, keeping her eyes on Erandur should the abyss take him over. She didn't want to hurt him, that was clear. She was afraid of the Abyss spreading further.