Malthus
Malthus is a hollowgast that kills Martin and that attempts to kill Jacob, Emma, and other peculiar children. Like all hollowgast, Malthus has rotting flesh and tentacles spouting from his mouth. Jacob is able to kill Malthus using a pair of large sheep shears.
Dylan
Dylan is a boy who lives on Cairnholm in the present day. He and his friend Worm prank Jacob when Jacob asks them to lead him to the home, bringing him to a shack full of sheep excrement before abandoning him.
Martin Pagett
Martin is a museum curator on Cairnholm island. Towards the end of the book, he is found dead in the ocean with severe wounds. When Enoch revives Martin, the children discover that he was killed by a hollowgast.
Olive
Olive is a peculiar who lives in Miss Peregrine’s. Her talent is that she can levitate, and often the other children have to tie her down to furniture or keep her on a rope outside so that she doesn’t float away.