Speaking of Midgardsormr, I've always wondered if the Battle of Silvertear Skies might have been classified as a Calamity in any other situation, since it changed the aetherial landscape on a wide scale. It apparently made the summoning of Primals much easier, which, in the absence of Echo-blessed adventurers, would have been a lot more damaging than they ended up being.
And then Bahamut happened, which changed the aetherial and physical landscape on an even wider scale.
And then Bahamut happened, which changed the aetherial and physical landscape on an even wider scale.