It's from Final Fantasy XIV. I swear I've heard a battle/dungeon theme of this song (https://www.youtube.com/watch?v=m38wQdh6Je0) before, but I can't seem to find it anywhere. Anyone know it? THIS (https://www.youtube.com/watch?v=Ytsmmrs29gc) song also has parts of it, at around 2:38.

Found it! It's the instance theme for Keeper of the Lake, "Silver Tears."
https://m.youtube.com/watch?v=JTfxjRuEfLw

In case anyone is wondering, it's track #60 on the "Before the Fall: Final Fantasy XIV" album.