Adam was in the dream, too; he traced the tangled pattern of the ink with his finger. He said, "Scio quid hoc est." As he traced it farther and farther down on the bare skin of Ronan’s back, Ronan himself disappeared entirely, and the tattoo got smaller and smaller. It was a Celtic knot the size of a wafer, and then Adam, who had become Kavinsky, said, "Scio quid estis vos." He put the tattoo in his mouth and swallowed it. - Maggie Stiefvater, The Dream Thieves.