Sif honestly wasn't sure what she'd been expecting out of Harry's magic to be honest. Magic itself was a thing she knew, a thing she was more than comfortable with the existence of, but its practice had always been something she left to others. What she'd seen so far, coupled with his willingness to come along on this journey into madness? That was enough for her to put faith in him, to believe that she wasn't at risk despite the sights set in front of her. She'd simply stand her ground, swinging the sword down hard into her shield to draw as much focus to herself as she could and, when the monster leveled its arm in her direction, simply held her breath while the display unfolded.
And she was not at all disappointed. She even smiled for a moment again, at least until she caught the sound behind her. A quick look over her shoulder, seeing that Harry was on his hands and knees, and Sif stepped back to form a wall between him and whatever would seek to come down that hall next.
"Catch your breath Harry Dresden." Sif braced, one foot in front of the other.She kept her eyes locked forward, waiting for the ruin of bodies to be cleared by the relentless assault of what she was sure would come next. "Our allies must surely be close to their goal by now and then all we must do is make our way back to the TARDIS." She tried to keep her voice even. She knew, all too well the dangers of a faltering resolve and, even if something told her she should not be concerned about that in this case, she still wished to offer the comfort to the man on his knees behind her. "And then we will see you returned to Knowhere where we may drink and feast and tell a great many tales of your heroics." It was a promise as much as the other woman could give at the moment and one that would be marked by the narrowing of her gaze as the next wave of enemies began to make their way forward.
Sif knew this battle was one of attrition now, that the Reapers would win solely by numbers if nothing else. The plan to strike them swiftly and at their hearts had seemed brash to her at first but now, being inside the beast, she was beginning to understand the nature of its creation. She was battle tested across the whole of the Nine Realms. She had helped bring peace and civility to all of them during the upheavals that had plagued them. She knew what it was like to battle for days on end with no respite in sight -- and even still the prospect of this battle concerned her more than she would have let on.
"Conserve your strength Wizard." Because that was going to be his name forever now, a token of her approval if nothing else. "I will make certain not a single foe reaches you." She shot a glance over at Torunn and gave a nod to Harry briefly. "Stay behind the girl." And with that, Sif sprinted forward with a furious battle cry and launched herself into the sea of enemies where she might hold their attention until the battle was won. It was a fray that would see her scorched by explosions of enemies and, despite the shrill cry of panic such a thing drew from her lungs, remain undaunted in her resolve to slay them to the last, or at least buy her allies the time they needed to complete their mission and rend the life from this Monster and its armies.