I’m a little late to jump on this train, but I just saw the earlier comment about what the “Charizard” equivalent would be - and I’ve recently taken a bit of a dive into whether or not there are any actual chase/rare cards and you’d be surprised to learn there are a few! (At least I was!
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But they’re not set cards, they’re promos - specifically 3 Japanese promos and 2 English promos. In order of rarity (from most rare, to least rare):
Devil’s Snare English w/Promo stamp
Back Fire Japanese w/Promo Stamp
Through the Trap Door Japanese w/Promo Stamp
Wingardium Leviosa Japanese w/Promo Stamp
Meeting Fluffy w/Launch Stamp
Devil’s Snare is a promo from the last set, so it’s quite scarce. I know the Japanese Wingardium Leviosa was a Corocoro release, there’s even a few sealed copies floating about. And Meeting Fluffy was included at the prerelease for the Adventures at Hogwarts set and has a really neat little stamp of the set symbol (the castle).
Overall, cool stuff. I’ve only seen the last two on the list, and I’ve been keeping my eye out everywhere for the other lot. I’ve included photos below 
