Note: In the examined copy (of first ed., first printing), 8 unnumbered pages as two bifolios of glossy stock, sewn to the binding between the fourth and fifth of eight gatherings that constitute the rest of the book--thus an eight-page centerfold in effect. Detail contents: eight full-page color portraits of characters: Thalia, Hal, Luke, Annabeth, Percy, Piper, Leo, Jason. The main human or demigod characters of the Heroes of Olympus series are all represented in this selection so it is likely to be uniform in all copies. Compare The Demigod Files (character illustrations), also 8 unnumbered pages featuring color illustrations by the same artist.