Every volume apparently included a promotional Japanese-language MTG card, many of them classic staples such as Shock, Worn Powerstone and Counterspell (MTG Arena Zone has published a full list, by volume)
For example, damaged copies of the Latias Star still command over $275, setting the market price for this card
One has additional space between the artwork and the long crimps and is noticeably longer
(Thankfully you can check how many you currently have by checking in your card collection.) Here's the card you'll need to collect 100 times for 'A Sweet Party of Epic Proportions': x100 Milcery #36 (One Diamond) Reward: Alcremie Emblem Extradimensional Crisis Museum 1 'Extradimensional Crisis Museum 1' tasks you with collecting six specific Full Art cards, including Celesteela and Alolan Meowth (a rather sassy-looking version of Meowth too)
You can pick up your card for next turn, cast the Tiger, and likely find a spell in the next two cards to keep pressure onand if you keep the Archangel, seeing two lands is still fine
They are unsuitable for collectors as these cards have a unique back design and are not tournament-legal