"Aww, even though we've barely spoken, you already know me so well," he said with a big smile, lifting his paw higher so she could take the bauble, "You're right, I do love shiny things," and yet, up keeping a certain reputation was important to him as well, especially if it made him more attractive to the ladies.
Just then, he heard a noise, or thinks he heard something. Peeking out over the ledge, Matthias' smile would drop a little when his gaze fell upon the approaching gryphon. It seemed to have a new meal in its clutches; a heavy buck that weighed it down. It didn't seem to notice them yet, "Um, I think we should skedaddle... The gryphon's here," his ears folded back. An angry gryphon is deadly, especially once it finds out its home has been invaded and its precious trinkets stolen. With a little more urgency, Matthias went back into the cave and said to her, "We gotta go now," and with that, Matthias would sneak out of the den, hopefully alongside Urna. If they were lucky, they could disappear just before it got here.
Giving you the opportunity to end it here if you want; we could say they escaped from the scene unharmed, or we can continue with a possible fight, or escape and Matt and Urna interact some more. Up to you!