Given that there was just the two of them, it was unlikely that magic would have been a good choice. The sword he had wasn't exactly Niren's, but it was good enough and the objective wasn't to kill Lust, just injure her enough so she could regain control. Maybe. He wasn't sure how this could go down, but he couldn't abandoned her when she needed him. Lunging forth, he thrust his sword at the elongated tentacles and attempts to stab at them. That should have taken up their focus so that Mikleo could do what he needed to.