So I've been thinking about something, and I wanted ya'lls take on it.
Probably don't read this unless you've at least finished the quest "One for the History Books"
Spoiler: Nergigante
Show
We've been told that Nergigante only shows up during the Elder Crossing, we know what the purpose of the Elder Crossing is, and the first two times we see it,
it almost seems to be protecting Zorah Magdaros. With this in mind, what if Nergigante is like Charon/the ferryman of the Elder Crossing?
It protects the elder dragons on the way to their final rest.
I haven't gotten to the point where I actually hunt it, so there may be more to learn that I haven't yet. But that's what I've been thinking.