Excellent and epically arranged.
You had a great trumpet opener which flowed into the Twins of Duality low piano beat. Also, I don't know if it was intentional (if so, truly excellent), but did I hear some bell tolling from HFX's Organ Jaws?
As SCTE3 mentioned, upon hearing this, it does sound like something that would be in an epic last boss fight. Especially so with the lead up at about 1:50, heading into the trumpets at 2:10, and ending with your voice-in.
At 2:50 (something I completely missed the first and second time I listened) was your own take on the high piano part from the second aspect of the original song. I also liked, how, at 4:14 you stopped the main part of Twins of Duality to add in, effectively, your own piece of work. This was well done and seems to fit the placement very well (again going back to the epic fight aspect of it being finished and heading towards the credits)
Finally, at the very end of the song, upon going back to the Twins of Duality piano opener.... it made my jaw drop because of how unexpected and masterfully done it was. Again going back to the epic boss fight.... it leaves a little bit of a door open to the listener to imagine that, just maybe, this isn't the last fight after all.
And lastly, some criticism... at 3:39, you softened the main theme from Twins of Duality and had other incidentals going on in, supposedly, the background. I think that if you would have softened the main theme a little more and also increased the incidentals, there would have been a bigger impact. Especially so heading into the piccolo part at 4:04 and your own piece as I've already mentioned above.