Just because he thought Artie Shen was only capable of mewling and whining out of embarrassment, Larkin didn't realize that the angel was indeed capable of violence. The moment she erupted from his teasing, she quickly pulled back her head and bashed it against his in a swift motion.
She even turned into a rat afterward, making Larkin deal with the sore on his own.
He was able to hide it from the chancellor as the sun was yet to rise. The darkness had become his friend, but the rat continued to just lug around. After the graces, the rat still wouldn't change back to its adorable form, and so Larkin thought of shaking it to rid it of the effects of its magic. He didn't bother using his own magic as it might harm the petty wife-to-be.