Modal double-faced cards were designed to allow both faces to be playable in all situations. For example, if an effect lets you cast spells from the graveyard, players expect to be able to cast either face. Feedback has shown us, however, that in situations where certain criteria are mentioned, being able to play or cast the back face when it doesn't meet those criteria is not intuitive. This confusion, plus being allowed to cast spells without paying their mana costs that you shouldn't be able to, makes cascade an issue.

As a result, we're tweaking cascade such that the spell you cast off the triggered ability must also have lesser converted mana cost than the spell with cascade.

Here is the new cascade rule:

702.84a. Cascade is a triggered ability that functions only while the spell with cascade is on the stack. "Cascade" means "When you cast this spell, exile cards from the top of your library until you exile a nonland card whose converted mana cost is less than this spell's converted mana cost. You may cast that spell without paying its mana cost if its converted mana cost is less than this spell's converted mana cost. Then put all cards exiled this way that weren't cast on the bottom of your library in a random order."

For example, if you cast Bloodbraid Elf and exile Valki, God of Lies from your library, you'll be able to cast Valki but not Tibalt, Cosmic Impostor. On the other hand, if you exile Cosima, God of the Voyage, you may cast either Cosima or The Omenkeel, as each face has a lesser converted mana cost than Bloodbraid Elf.

This change isn't limited to double-faced cards. It also changes the way cascade works with anything that has a "dominant" set of characteristics, like the Adventurer cards from Throne of Eldraine. For example, if Bloodbraid Elf causes you to exile Fae of Wishes, you may cast Fae of Wishes, but you may not cast Granted.

Finally, the interaction between split cards and cascade is unchanged; the converted mana cost of a split card is the total converted mana cost of its halves. If you cascade into a split card with lesser converted mana cost than the spell with cascade (remember, count both halves), you may cast either half without paying its mana cost.