Necromancy

Personally, I think it's harder than most 21s. It's still too tough even now.

It's definitely harder than ESM, JANUS, and DUOLDA

From the start, the leg strength requirement is beyond a 20, and the stamina drain is extreme every time you step through a section. At least a mid-low 21.

If you can handle the dragging and mashing in the late-game patterns of Necromancy s18, this isn't a very difficult song.