The False God of Causality
Ys: Memories of Celceta
Falcom Sound Team jdk (can't find specific credit)
The Ys series has gone through a lot of changes since its roots on the NEC PC-88. The music included. There are elements of the original style in the driving percussion, but the grandiose orchestration of this piece is a far cry from something you'd find in Ys I or II. It works really well, considering the circumstances when it's played.
The comments on the video I found of the piece compare it to One-Winged Angel, but I don't think I'd put it in the same category. This piece wants to convey a completely different mood than One-Winged Angel, and trying to compare the two is not very useful.
The False God of Causality sounds like a heroic climax of a movie, when the good guys have finally started to push back and gain footing against the bad guys.
#FelthrysVGMSelection
In contrast, One-Winged Angel conveys a sense of hopelessness, of overbearing power. It's not trying to achieve the same thing, and I think comparing the two is missing the point.
Final boss music can have any number of different moods to it, from the hopeful and heroic to the dark and hopeless, and even, in rare cases, the calm and serene.