Cascade

Cascade is a triggered ability that was introduced in Alara Reborn. It returned in the Chaos Reigns deck of Planechase 2012, in Modern Horizons, in Commander Legends, and in Modern Horizons 2.

Description
When you cast a spell with Cascade, exile cards from the top of your library until you exile a nonland card whose mana value is lesser than the cascading spell. You may cast that card without paying its mana cost. Then put all cards exiled this way that weren't cast on the bottom of your library in a random order.

Cascade was printed exclusively on multicolored cards until Modern Horizons, which featured the monocolored Throes of Chaos. Unstable had one monocolored cascader - also red - in a variant of. More monocolored spells with cascade followed in Commander Legends, which also featured the first colorless spells with cascade (Maelstrom Colossus and Ingenuity Engine).

Rules update
In February 2021, Cascade received a rules update to change the interaction with MDFCs and Adventure cards. From that moment on, the spell that is cast off the triggered ability must also have lesser mana value than the cascading spell.

The rules previously said "You may cast that spell without paying its mana cost.", allowing players to cast a spell with a higher mana value attached to a card with a lesser mana value. The rules change clarifies "You may cast that spell without paying its mana cost if its mana value is less than this spell's mana value.", making this no longer possible.

Rulings

 * Cascade triggers when the spell that has it is cast, not when it resolves (that is, before the permanent would enter the battlefield).
 * Here's the timing for cascade:
 * 1) You cast a spell with cascade.
 * 2) The cascade ability triggers and goes on the stack on top of the original spell.
 * 3) The cascade ability resolves. If you find an applicable card that you'd like to cast, you do so.
 * 4) The spell you cast as a result of the cascade ability resolves.
 * 5) The original spell resolves.
 * For the most part, cascade is mandatory. You must exile cards from the top of your library, even if you know that you won't exile anything you want to cast. Whether or not you cast the last card you exile is the only optional part.
 * The spell you cast as a result of the cascade ability resolves before the original spell. If you cast a creature spell with cascade and then cast an Aura as the result of the cascade ability, you can't enchant that creature with it because the creature spell hasn't resolved yet.
 * Cascade won't trigger if you put a copy of a spell with cascade on the stack (due to Cloven Casting or Twincast, for example). That's because you didn't cast the copy (such as with Isochron Scepter).
 * Countering the original spell doesn't counter the cascade ability.
 * Since cascade is a triggered ability, anything that interacts with a triggered ability (such as Stifle) will interact with cascade.
 * All players can see the cards you exile as the cascade ability resolves.
 * If you cast a card this way, you cast it as part of the resolution of the cascade ability. Timing restrictions based on the card's type (such as creature or sorcery) are ignored. Other restrictions are not (such as "Cast [this card] only before attackers are declared").
 * A spell cast as part of the resolution of cascade is cast from exile, not from your library. Abilities that prohibit you from casting cards from your library (such as Grafdigger's Cage's second ability) will not stop you from casting a card with the cascade ability.
 * If you cast a card "without paying its mana cost," you can't pay any alternative costs, such as evoke or the alternative cost provided by the morph ability. If it has X in its mana cost, X must be 0. However, you can pay optional additional costs, such as conspire, and you must still pay mandatory additional costs.
 * A card cast with cascade behaves like any other spell. It can be countered. If you cast another card with cascade this way, the new spell's cascade ability will trigger, and you'll repeat the process for the new spell.
 * Casting a card with the cascade ability is optional. If you choose not to, the card is put on the bottom of your library in a random order along with the other cards exiled with cascade.
 * If you cast a spell with cascade and there are no nonland cards in your library with a lesser mana value, you'll exile your entire library. Then you'll randomly rearrange those cards and put them back as your library. Although you're essentially shuffling those cards, you're not technically doing so; abilities that trigger whenever you shuffle your library won't trigger.

Enchantments

 * Maelstrom Nexus</c>

Creatures

 * Yidris, Maelstrom Wielder</c>
 * The First Sliver</c>
 * Imoti, Celebrant of Bounty</c>

Trivia

 * Maelstrom Wanderer</c> has "Cascade, cascade."
 * Apex Devastator</c> has "Cascade, cascade, cascade, cascade"
 * Cascade was featured as rules card 2 of 3 in the Alara Reborn set.
 * Cascade was considered to be a design failure by Aaron Forsythe because it did not play out as randomly as the design intended. The biggest culprits of this were the costless Suspend cycle in Time Spiral - Hypergenesis</c>, Living End</c> and Restore Balance</c> all made for decks reliant on using Cascade as casting tutors, and the Hypergenesis deck was strong enough to be banned.
 * The Heroes of the Realm card features Booster Cascade (It’s like cascade but you use your booster pile rather than your library.)