" Right,' he said. 'So it stands to reason there's something about the line that fortifies or protects a corpse. The soul. The ... animus. The quiddity of it.'
'Gansey, seriously,' Adam interrupted, to Blue's relief. 'Nobody knows what quiddity is.'
'The whatness, Adam. Whatever it is that makes a person who they are. "

― Maggie Stiefvater , The Raven Boys (The Raven Cycle, #1)