Trilogies and Tetralogies

This weekend my wife and I will be at Gaelcon, the largest gaming convention in Ireland. I typically run a roleplaying game at the convention. Since running rpgs features a lot of consideration for story structure and offers a great proving ground for plot ideas and usage of themes and tropes, I thought I'd spend this week talking about certain aspects of storytelling structure.

For today's post, I'm dealing with two of the most common series formats, the trilogy and the tetralogy, going all the way back to ancient Greek theatre.

Ancient Greek theatre was often crafted and performed in a 3-play format. We get our term "trilogy" from this, when audiences would spend a day at the theatre, seeing three tragedies forming one over-arcing story, accompanied by a more comedic "satyr" play.

The trilogy has remained with us to this day, becoming the most common form of storytelling in any genre and format. Even within standalone novels and movies, we talk about the 3-act structure. In a typical trilogy today, the first story will handle the introduction of the heroes, the villains, and establish both the state of affairs from before the beginning of the story, and a new status quo after the villain's defeat. The second story further develops the nature of the heroes' struggle and often reveals more of the villain's motivations, often culminating in an ending that pitches the heroes into their darkest hour. Finally, the third part of the story will bring elements of the previous instalments together as the heroes come to their final realisations, unlocking their true strength and finally overcoming the villain.

A four-part series is properly termed a tetralogy, coming from the Greek "tetra." When the trilogy of tragedies in Greek theatre is taken together with its accompanying satyr play, it forms a tetralogy. Unfortunately no complete ancient Greek tetralogy survives. The only Greek trilogy which survives is the Orestia. Recently movie trilogies have been revisited, turning them into tetralogies. Examples include the Rambo, Die Hard and Indiana Jones series. However the term quadrilogy, first actually recorded in 1865, is usually used instead when marketing 4-part movie series.

The structure of a tetralogy is more difficult to define. In planned 4-part series, tetralogies often eschew convention and while the third part may resolve many of the challenges faced by the heroes, the final victory will be delayed until the fourth part, or a previous lesser antagonist, or even an entirely new threat, may rise to challenge the heroes one last time.

Other formats of set series include a diology, pentalogy, hexalogy, heptalogy, octalogy, ennealogy and decalogy. These become ever more difficult to describe in terms of a predictable act structure, and usually become either more or less standalone stories connected by common characters and possibly an over-arcing metaplot, or simply one ongoing story broken up into component parts. In most cases, once a series has gone on long enough to move beyond five or six instalments, it can become difficult even for the author to define what kind of series it is until the final instalment has been released.

Do you have any favourite series? Is there a particular series length you find you prefer over others?