As Dean delivers his parting shots - both of them - Castiel strides forward, sword in hand.

It feels like a long time since he's felt his role as a soldier in this way. Philip doesn't even like him. But Cas wants him to. So he will do what he must to help him.

Calmly, unheeding of the blood getting on his clothes (he's had worse, far worse... Dean's insides working a shift as outsides comes to mind), he draws the blade back a little, and then thrusts it upward beneath the Shadow's ribcage, straight into its heart. Lightning crackles through its frame, wreathing it in sparks and light, and when it dissipates, the Shadow falls away as ash that disappears into the air, less than dust.

Castiel's sword can kill angels. The Shadow isn't coming back this time.