Definition from Wiktionary, the free dictionary
Imitation of trilogy.
octalogy (plural octalogies)
- (rare) # A set of eight works of art that are connected, and that can be seen either as a single work or as eight individual works. They are commonly found in literature, film, or video games.
- 1886 
- The Shakespearean octalogy which begins with Richard II. and ends with Richard III.
- 1886