@JaneJeon
It is usually used as a mark of death.
Other types of symbols I've seen are transformations or changes.
I'm taking an interpretation that sinceramente it's a dark one, and with a lot of details, it may mean a rotten butterfly, considering he is a butterfly (pretty), someone you would expect good things, he shows a rotten and sick side, he reveals himself as someone ugly.
Maybe I'm just overthinking tho