The term 'COOPER HERO' refers to the characters created by James Fenimore Cooper in his series of novels known as the Leatherstocking Tales. The three crossword solutions, UNCAS (5 letters), NATTY (5 letters), and DEERSLAYER (10 letters) are all characters from this series. UNCAS is a Native American chief of the Mohican tribe, while NATTY is a white man who was adopted by the tribe and given the name NATTY Bumppo. DEERSLAYER is the title of the first novel in the series, which follows the adventures of NATTY Bumppo and his friend, Uncas.