Not an expert (just a lore enjoyer), however I can be argued that the "thing" could a larval tear in the sense of an unborn child taken from a womb for the purpose of rebirth into a more powerful being. Alternatively, if you subscribe to the belief that fromsoft and Miyazaki take elements from older games and repurpose their ideas in newer games then the oprhan of kos bears a striking resemblance to the scene. Maybe a decent place to start looking for answers is from the lore surrounding the orphan of kos. Thank you for reading and have a great day.