Like all aspects of this show, this episode's going to be pretty controversial because of the continuity lockout: see Gotchard vs Legend was filmed in the beginning of production with Gotchard's earlier episodes, allegedly one of the earliest, hence why Houtarou's the only one in the cast who knew and was involved in those mini series, though the plans were to have Legend return in the show eventually.
In that special, Kaguya, Kamen Rider Legend was saved by Kamen Rider Decade, and via a promise to his dead grandfather, he ultimately decided to become Legend with his resources he amassed, and fights the Hundred organization in his dimension we saw from last episode: and as this episode shows, Hundred uses their technology to copy powers of Dark and antagonistic Riders. The special only introduced one of them, Gengetsu, and we saw the Kasshines they used as the foot soldiers last episode, Alpha was the captain but this idiot forgot to look that up.
It seems like the arguments online come from the fact that for some people this came out of nowhere and that you need to watch all the other content to get this. Honestly though, as someone who hasn't watched it's not that hard to get a grasp of what's going on here: there's another faction of antagonists out there with their own adventures and they just happen to cross paths with this world's protagonists. Plus the flashbacks give a good idea of the situation. Hell last episode we saw Butler designing the superweapon they're after that came to Gotchard's dimension.
And it feels natural: Houtaro vaguely remembers them, the King wants the Sisters to investigate, and the Alchemists have to deal with both factions wreaking havoc when Butler introduces himself.
The Door of Darkness got opened or leaked: best guest, given the inability to open the gate, the Abyssalis King Gigist probably used or retrieved enough intel from Geyron about the circumstances going on and used him as an alchemist conduit for a one time escape. Then again, Geyron's plans with the GotcharDriver was enough to open it from the outside, so the show will probably explain how he escaped later. Though speaking of that, it'd be a wasted opportunity if we don't see Atropos questioning if Geyron is okay, but she is the most pragmatic of the antagonists so for now it's fine.
So Butler and Kaijiki are played by the same person. Never learned that's feasible in production, but it's cool to have them both on screen, though it's funny to have Sabi/Isaac confirm it with a near 97% accuracy and everyone giving Minato the look because even their straight-laced teacher's super uncomfortable with that reality. It also helps the audience get introduced to Hundred: dimension invaded syndicate, and then we get the Aurora Curtain...
...which um, Decade has always introduced this filter of a dimensional warping portal, that never really a name. The Legend special was the first to give it a name...but this is the first we've heard it be said in a show, which is neat: it's always cool to see a current season build on what a past series has done before.
Tasogare, Mimei, and Saigetsu aren't going to be some deep complex villains, but they get enough of a personality: the former's the extroverted one, Mimei's just a sword lady of battle, and Saigetsu really likes to say scrap. They actually unironically fit in really well, Gotchard's Malgams have mostly been felons, minor criminals, abusive dads (funny how Geyron's not the only one).
Though as they're telling the hero trio about their plans to send more of their soldiers in through the Aurora Curtain's complete opening, the translation has Houtarou calling it Panna Cottas. Now Houtarou being book dumb is consistent, aurora and curtains are not hard to remember, but the fact food was on his first mind: panna means cream and some chefs were cottas it's just a fun nod to his mom's business.
We're getting a lot of hand to hand action in this episode even before the transformations: wonder who's directing this episode and last one: oh Koichi Sakamoto, that makes way too much sense.
Fun fact, for the dark riders, they contacted their past actors to help them make deviations of the characters henshin they are resembling, and even make deviations of their respective catchphrases. Mimei doesn't get one because Glare didn't really have one under Girori's usage: didn't really fit that character but Tasogere uses Eternal's "now have a little taste of hell," and Saigetsu uses King's "It's extinction time."
Lachesis becoming Valvarad is cool, she's kissed before in fights, but using it to transform into Valvarad Warrior is a good fit. The green lines are cool, wonder if they were a nod to her using more Green and Plant Chemies in the past: and it's cool she had leftover Repli-Chemy cards.
One thing that might piss off some people is Gotchard fighting them in his base form and then uses it later but in his defense, fighting an opponent you don't know that much about doesn't give you a set idea on what their power is, and once you know, then you can use the later forms. It can be annoying to some but in this case, it doesn't bug me too much.
Will say the range between the actor does going from a everyday mystery buff in high school Kajiki to the elegant Butler is a cool thing to do.
While cool to see X-Rex, Gotchard's more aggressive form take on the brutality of Dark Kiva and Eternal, Houtarou vs Tasogare actually gives Houtaro a good character beat, Hundred's Kamen Riders are stealing, well borrowing the powers of Kamen Riders from other worlds, and ties into a problem often coined in fandom spaces as dangling keys:trying to entertain the audience with familiar elements like jokes, past references, or nods that aren't new or come off uninspired, and this episode had people criticize this episode for doing that with it's past nods and references. Houtarou's response honestly puts a statement like that into question. While it's a cool nod to the older fans, Gotchard's characters have built up and struggled their their fights with their Chemies to get the power that they have, so they arent' going to lose to pale imitations of people just using past. The Chemies aren't tools, but how you raise and nurture them decide who they can help, who's hatred they'll feed in, just like Rider powers our. They can be used by good people, as well as bad, and it felt the message was not to dissuade the past in the present, while carrying on their ideals.
We even see Houtarou using FireGotchard with Ant Wrestler, a Chemy he had an whole episode.
For example: Mimei actually uses Glare's control effectively, taking control of another character to harm their allies, and it was a big deal in Geats because it eliminated Ace from the Desire Grand Prix at the series, and it lead to him nearly dying in a "taking you with me," and Mimei's attempts to do that was almost replicated, but Lachesis interferes, Valvarad decides not to let that shock interfere, and then of all people, Clotho activates her Abyss Gear and fights all four Riders at once before freeing Rinne. The new characters aren't just here to make the audience go "look at this from the past," they have their own stories and arcs to pursue: the Double Riders finishing off with a join Valvara/d Rider Kick Break and Crush: two people who used to hate each other, now begrudging allies on the battlefield. Even though it was a wasted opportunity to have Spanner slowly come to appreciate her involvement in the fight.
And it's a sweet continuation of Clotho's power: she got it from her desire to protect Lachesis, so for now, why would she hurt her sister. It sucks Majade has to take the L, but it's a good debut for the type of power Clotho can possess and it shows the fun in having three factions of opponents all with their own intentions.
Oh hey, it's Zein from Kamen Rider Outsiders: long story short, he's one of those "must eradicate all forms of evil, even if that evil isn't that bad or the situation is more complex AI" that a suicide squad esque type of Kamen Riders from the past have to deal with, minispecial. Don't know if he'll show up again in the series or if it was a promotion, but Outsiders ties into the main universe, but it is funny he calls her a fraud: cuz yeah, Hundred's a bunch of copycats.
What's really appealing towards Iron Gotchard's defeat and Kajiki finding out Houtarou's identity again is the crowd behind him and Houtaro running to get the innocent girl out of the way. Kamen Riders don't inherently fight for justice, but at the end of the day, they fight for human lives: the speech Houtarou gives about small life not being true: that human, Chemy, no life is worth not protecting. Everyone behind him matters in some way or form, Kamen Riders are what give the people hope in the world against evil, like Superman. And the cheers of the people, picking him back up are representative of what Kamen Riders truly are: those using powers potentially for evil to cherish all lives. It's why using Platinum works better now than in the beginning: that's a form made by Houtarou's connections built off two creators and the guidance of his human allies motivating the others to work with him.
Plus there's a great nod with the final clash, Eternal uses the Zone Memory to activate the Maximum Drive and Eternal by using all 26 Memories for Eternal's finishing move used in the past, Gotchard uses TWENTY SIX Chemies whose names begin with A to Z into one massive Rider Kick. He won't lose to someone whose power is stolen from others.
Also fun fact, they didn't have a direct Chemy whose first letter began with Q, so they went with the one with the closest sound: Hiikescue,
Kaguya showing up to destroy the Aurora Curtain and debuting his main forms, cycling through the first 10 Heisei Riders and using the superweapon that was sent to Gotcahrd's word last episode, a Chemy Card to transform him into Legendary Legend...yeah the name is a lot, but for a gorgeous end to the episode, it's a fun way to end a fun episode.Overall, it's a good episode that doesn't use nostalgia bait, but respects the past while continuing to move the story forward just having heart in an action focused episode.