Ok... So, Kamen Rider Saikou is going to be a Sword and not an actual Rider. He is called Kamen Rider because you know Toei has plans to bring his actual Kamen Rider forms in the future just to sell more toys.
Currently, the sword form is called "Kamen Rider Saikou Kougou-Ken Saikou". Yeah, Kougou-Ken Saikou is the name of this Seiken and to transform into this form, he'll use "Kin no Buki, Gin no Buki" (Golden Weapon, Silver Weapon) Wonder Ridebook which is inspired from the story of "The Honest Woodcutter".
Kougou-Ken Saikou can float in air in it's own will and can summon a Shadow warrior from shadow to hold him during the fight. This shadow warrior is called "Kamen Rider Saikou Saikou Shadow".
If Ultraman Z's suit actor Hideyoshi Iwata is going to play Shadow, then maybe we'll get to see Beliarok - Ultraman Z type of conversations scenes between the Sword and the Shadow.
Touma will also get a chance to use Kougou-Ken Saikou which is basically Kamen Rider Saikou.
Touma will fight against Kamen Rider Calibur. He'll transform into Crimson Dragon and also Kamen Rider Saber Dragon Alangina and finally into Dragonic Knight. In order to avenge Kento, he will also use his Raimei-Ken Ikazuchi. With the Final Blow by Dragonic Knight, Calibur's transformation gets removed.
Desast appears and kills Kamijo from behind. Touma gets near him. Kamijo gives the Ankoku-Ken Kurayami to Touma, but it disappears as smoke.
The four Swordsman → Blades, Buster, Kenzan and Slash attacks Touma thinking that even he will betray Sword of Logos. That's where Yuri / Saikou comes in to save him.
Some of the new scans from Kamen Rider Saber Short Film featuring Kamen Rider Saber Emotional Dragon.