Complex sentence: ' Miss Wren is hiding in a building coated in thick ice to prevent wights from entering and proceeds to help Miss Peregrine retain her human form once again, which she estimates will take the whole night.
Split into simpler sentences: ' Miss Wren who is hiding in a building coated in thick ice to prevent wights from entering. She proceeds to help Miss Peregrine retain her human form once again, which she estimates will take the whole night.