[DreadBringer]

Kaguya has the usual secondary Rider conflict/miscommunication here where he acts hostile towards his allies by attacking Houtaro, but it's actually his way of keeping them out of trouble so he can handle problems alone. His flaw is that he struggles to communicate well and positions himself above their level.

After the base form resembling Decade, Legend's final form, Legendary Legend powers resemble another anniversary Rider, Zi-O. He can summon Riders alongside him rather than becoming those Riders. For main series stuff, Gigist merges Chemies with Ark-One to form a Malgam, and Gotchard has a rainbow force field to protect himself, which becomes important later in the story.

Gotchard Daybreak's return also confirms that he didn't perish after guiding Houtaro back in episode 18. His disappearance wasn't due to the future being rewritten but because the TimeLord running out of time.