I don't understand how Age of Calamity got roped into this discussion. It's a Hyrule Warriors game first and foremost and therefore not a sequel to Breath of the Wild. To consider it a legitimate part of a trilogy to a completely different genre of games is absurd. Tears of the Kingdom is a sequel to Breath of the Wild, not Age of Calamity.
Age of Calamity is a very strange case, as it is canon and yet contradictory.
Ganon awakens and triggers The Great Calamity.
Terrako goes through a time warp into the past in order to try to warn the people of what is about to happen and protect Princess Zelda.
However, events clearly do not line up with Breath of the Wild's backstory events.
- Link acquires the Master Sword in his late teens and not his early teens
- He is a typical knight within the ranks and not a notable character that the royal family has kept their eye on over the years
- The Champions are being assembled within a week of the Great Calamity instead of months in advance
That's just a few contradictory details that Age of Calamity has to offer.
But despite these contradictions and such, Nintendo has declared this game as Canon.
And I think I know how.
It wasn't just simple time-travel. It was an artifitial form of time travel made by mortal hands and not with the aid of a deity that has control over time. The two Gates of Time was created by Hylia and her worshippers. The Harp of Ages is a divine tool to be wielded by the Oracle of Ages. Teh Ocarina of Time is a tool that allows the user to restart a timeloop.
Meanwhile Terrako does something different.
Not only does this little robot drop into the past, but the simple act of doing so has a ripple effect that streteches through the timeline.
A Timeboom.
Terrako's method of time-travel is a different method than what we have seen previously in the series. By going only a week into the past, a ripple was made in time that saw events prior to the little robot's arrival into the past be altered in minior or major ways, all while not really changing the major course of history until we reach the point in time he little Guardian arrived to the past, in which all events afterward begin to have major differences from the main timeline.
Hence why Link is just a typical knight and that the Champions are not yet assembled.
History plays out mostly the same between Breath of the Wild and Age of Calamity, only some details are altered.
And with everyone acting with new information from the future thanks to Terrako and Corrupt Terrako's actions, it leads to an entirely separate outcome than the events we know from Breath of the Wild.
Add ontop of that the next generation of Champions being warped in from the Future, and you have further shenanigans with the timeline.
Hence why I like to refer to this new alternate timeline that Terrako caused by warping back in time as "
The Terrako Paradox".
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To answer the question of "Is BotW a Trilogy", the answer is currently no.
There are three games in the lineup but one is a spinoff and not a main-line game that is tied to the direct narrative of the game.
Should Nintendo make a third game set after Tears of the Kingdom OR make a prequel game in which we play as the Hero of the Calamity depicted in the Ancient Tapestry, THEN it would be a Trilogy.
As it stands right now, it is a dual-story narrative with a bonus "what if" story attached.
The term for this is a Diptych.
Not a Trilogy