Now that is what I call a boss fight! And even an intro and a 'you win' effect at the end, beautiful additions! I love how you made a 5/4 -> 6/4 -> 5/4 -> 4/4 work, it just shows that you can make everything work with a little skill!
The song has enough power to be considered a boss-fight (even with time-sig changes). The instruments give it, as you call it, the perfect 'medieval feel' which I agree with. Furthermore, cool melodies and chord progressions make this my absolute favorite so far!
Well done <3
EDIT: after watching the video since people appeared to be loving it: that's hilarious! Nice effects too. Simple but effective :)