I've listened to some Final Fantasy music in general, though I've never played any FF game. I have the full soundtrack for 7, I listen to some of 8, I like Kefka's theme...
But overall, I got a certain feel from them, that they had a sort of, not exactly predictability to them, but that when there was a boss to be fought, you'd get "Boss Music," a track that felt suitably charged and epic for this encounter.

Now like I said, I haven't played ANY FF game, or seen much of anything about FFXIV, but I still had that idea in my head of what any boss music would be like.
And then a friend had me listen to the boss music for fighting Titania, "What Angel Wakes Me"
https://youtu.be/saYCZ9jzLEA
It starts off with strings and a piano making a kinda stomping intro, I thought it'd continue as normal
but it gets so delightfully weird

I love the strange, ethereal feel to the music, considering Titania is the Queen of the Fae (i don't know how different it might be in FFXIV)
And the whispered lyrics, somehow feeling rushed, frantic, but calm, the words describing something vague enough... it almost feels like the song itself is like, some part of a fae ritual
It's really amazing, and definitely a favorite of mine <3