So I just found out the 2 elites in co op in halo 3 are actually characters in the halo universe and not just some random guys from reading the book hunters in the dark. I wish they made this more apparent in halo 3. This book also feature veil from fire team osiris. These 2 are really interesting characters and hopefully will make an appearance in halo 5. Left the urls for there wiki pages if you wanna give them a look without reading the book
edit: would you like to see them return in halo 5?