After 20 episodes of mostly screcy, this one was a massive infodump.
So Sakura herself is creating the new cards out of however she's feeling at the moment. That's a theory that had been around for some time since the new cards always seemed to be related to whatever Sakura was thinking about at the moment. The questionable names are because Sakura still sucks at english, a point hammered down multiple times by the anime. Of course Sakura's basically oblivious to this, although in this episode at least anime Sakura did notice the "new" card has the same name as one of her previous cards. And looks literally the same besides a pair of new horns.
Sakura being able to create her own cards just out of her feelings was one of the major end points of the original series. She's become that powerful of a mage. Granted, the other time the card popped right in front of her, but I guess it evolved.
More interesting, Sakura created her first original card because Syaoran was about to leave... And then starts creating them again only after Syaoran returns to stay in Tomoeda for good.
Basically everybody else that can use magic seems to have realized the "secret" already, but they didn't tell Sakura to don't worry her. Because quite literally making the mighty magician worry may make her spawn something terrible. Just like the Mirage card episode had everything getting worst because that, just by imagining how things could get worst, Sakura just made it so. The best they can do is keep Sakura thinking about sunshine and sweets and rainbows and keep her away from any post-apocalyptic media I guess. And even then the sweets can go wrong.
Sakura's not that stupid anymore though, she's realized Syaoran in particular is not showing his full hand either, just been playing nice because she trusts him but still finally calls him on it.
Really gotta had it to CLAMP, they did manage to make a proper sequel after all.
Also Nadeshiko's may've been a magical girl too? She somehow manages to warns Sakura to turn back when she peeks too much into the past, probably because Sakura may just accidentally tear the time-space fabric or try to join her mother in death or something even worst.
Fujitaka reveals he's not blind and did notice his daughter's been having troubles since the original anime but somehow realized he couldn't actually help about them so never brought the issue up to Sakura. I still remember that time whe she broke his laptop and Fujitaka was all "nah, that's fine, don't worry".
Also confirmation that Eriol's house had been torn down to build an amusement park as per the 2nd movie, but nobody but Eriol remembered that. Guess that there's some spammable mass mind-altering spell being used in the public. Maybe Sakura unconsciously makes any random strangers who sees her flying around Tomoeda forget? Tomoyo has a really good will save and succeeds?
Sakura sharing her flight magic with Syaoran animated was pure cuteness overload, in particular when Syaoran hugs her in the sky.
Also clock butler is the villain. Because of course there was a magician association all along that seemingly ignored the 2 or so years Sakura spent collecting the Clow Cards. Clock butler stole an artifact (most certainly the book Akiho keeps carrying around, which Sakura did saw and found it suspicious and then promptly forgot it) and he wants Sakura's new cards to power up something.
However the robbed figure we've been seeing seems like Akiho herself, those being the traditional robes of her family, and the big black dragon does seem to resemble the clock butler's clothing.
Still doesn't exactly explain why or how the Sakura cards got sealed.
Speaking of which Syaoran seemed to be using Windy himself some episodes earlier.
Syaoran is revealed to have placed a spell in the plushie he traded with Sakura that allows him to somehow syphon the sealed magic of the Sakura cards. Not only that, we can see that where the cards previously had little stars on them, representing Sakura's star magic, they now have little moons, representing Syaoran's own moon magic.
In one hand just
borrowing your own girlfriend's magic seems kinda of a dick move, even if he claims he will use them to protect Sakura (and indeed he seems to only have used them to support her in battle).
In the other hand Sakura was just keeping them locked up, and we know the cards are sentient to a degree and like getting a chance to do stuff, so good job letting them get some fresh air?
And then the mysterious robbed figure turns out to be Syaoran: Ah, wait, it was all just a dream. From the magical girl that can see the future in her dreams.
Popular theory seems to be that it's clockwork butler messing with Sakura's dreams, but then in the dream the hooded figure does try to take her magic, and Syaoran is syphoning the Sakura cards, so welp, we may be about to see their first couple fight.