Presumably, you can also take things out of those worlds due to the appearance of the magical object in Ariels artwork, along with item cards such as the Stolen Scimitar and the Scepter of Arendelle
This was exacerbated at the end of 2024 when WotC announced that not only there would be 3 Magic Multiverse and 3 UB sets in 2025, but that UB sets would become Standard-legal for the first time
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Urianger Augurelt's last ability)
For example, the Masterpiece Series cards in Kaladesh and Aether Revolt will share one unique expansion symbol?they won't use the Kaladesh or Aether Revolt symbols
Maybe Dalmatian decks really will be a thing after all
Maybe it's because Hades isn't a princess