This is the only time Jun Senoue and Tomoya Ohtani have worked together on a song, and I wish it happened more often because it's so good.
Technically Jun Senoue has contributed his guitar playing skills for some of Tomoya Ohtani's other songs (the music for Infinite in Forces is a good example), and they've also arranged songs by each other, but this is the only time they've been credited as having both composed and arranged a song.
Ahh Nightwish. One of my first symphonic metal listens. It's really a blast. My favorite album is Oceanborn (I hear Wishmaster is excellent) but other albums have bangers tracks like Amaranth, Nemo, 7 Days to the Wolves, Master Passion Greed, Planet Hell, Moondance, Passion And The Opera, The Kinslayter and so many more.
Imaginareum album is a good one too (Storytime, Ghost River, Rest Calm, Scaretale, Slow, Love, Slow, I Want My Tears Back. and The Crow, The Owl And The Dove). Their older tracks had a more opera-singer-like lead singer (you're sharing one of the older ones). I also enjoy Dark Passion Play album too.
I also recommend checking out Epica for a similar style
And I have Krypteria too as a recommend;not as strong as Epica
but I can also recommend power metal like Rhapsody of Fire (which is focused more on shredding but has the similar chords and sounds medieval too) and too if you're in to that style, which earlier Nightwish albums take the style from.
There's a LOT of stuff out there; I haven't scratched the surface of symphonic metal or power metal. My metal tastes here vary a lot, I kinda listen to a bit of a lot from metal.