Well uh, from every single preview image and video shot of the final episode, it's the Rising Hopper suit.

Unless we get post VFX Editing in here and it's a different special coloration or aura. Or they pull an "All Hopper" card, in that the key just contains all Hopper Data and Aruto switches between all hopper based forms before ending it off where it all began with Rising and they're just showing us Rising's scenes to hide it.

I dunno man, Build and Zi-O both had final episode new forms.

I wouldn't be surprised if this key has some new kitbashed form.

Its definitely Rising Hopper, but the key recolor is probably there just to explain how it can beat Ark Scorpion.

The Zero One movie is gonna be releasing in December 18th, in place of the usual Rider team up movie. So I reckon the Saber X Zero One movie will release around spring time.
http://zero-one-kiramager.com/

Interesting name.

So, his debut is up on YouTube. He's another Ark rider.
Azu gave him the belt and key.

He uses a Human Progrise Key.

Interesting design and he have a neon purple color.

I wonder what's his agenda since most evil movie rider usually have their own agendas.

Similar to Ex-Aid, Look like Zero-One movie will take place after final episode and this guy look like the true final boss for Aruto and other riders.

Sentai movie taking place in spring makes it an epilogue return movie.