The Clown is a nameless male syndrigast with an unknown peculiarity who dresses up like a clown for reasons unknown.
While discussing matters of Miss Wren's army, the clown asks the children about their peculiarities, but comes off as aggressive. He discovered the Bone Brothers' peculiarity; when pulled apart, they emit an ear-splitting scream. This upset the other children as well. He only stopped when Bronwyn threatened him.
He, along with Sergei, tried to recruit them for their peculiar army.
He appears while waiting for "Miss Peregrine's" transformation and is later on caught by Caul.
He is not seen at the Wights' Fortress later on in Library of Souls, so it is likely that he was killed before the wights brought the rest of the captured peculiars there. Olive also tells Jacob that the clown was thrown into the pit by the wights for refusing orders.