Complex sentence: The blue men may have been part of a tribe of "fallen angels" that split into three tribes; the first became fairies, the second evolved to become the blue men, and the remainder the "Merry Dancers" of the Northern Lights.
Split into simpler sentences: The blue men may have been part of a tribe of "fallen angels" that split into three tribes. The first became fairies, the second evolved to become the blue men, and the remainder the "Merry Dancers" of the Northern Lights.