Sakashima's Protege — ruling 1

The mana value of a split card is determined by the combined mana cost of its two halves. If cascade allows you to cast a split card, you may cast either half but not both halves.

Sakashima's Protege — ruling 2

Cascade triggers when you cast the spell, meaning that it resolves before that spell. If you end up casting the exiled card, it will go on the stack above the spell with cascade.

Sakashima's Protege — ruling 3

When the cascade ability resolves, you must exile cards. The only optional part of the ability is whether or not you cast the last card exiled.

Sakashima's Protege — ruling 4

If a spell with cascade is countered, the cascade ability will still resolve normally.

Sakashima's Protege — ruling 5

You exile the cards face up. All players will be able to see them.

Sakashima's Protege — ruling 6

If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, you must pay those to cast the card.

Sakashima's Protege — ruling 7

If the card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

Sakashima's Protege — ruling 8

Due to a 2021 rules change to cascade, not only do you stop exiling cards if you exile a nonland card with lesser mana value than the spell with cascade, but the resulting spell you cast must also have lesser mana value. Previously, in cases where a card's mana value differed from the resulting spell, such as with some modal double-faced cards or cards with an Adventure, you could cast a spell with a higher mana value than the exiled card.

Sakashima's Protege : règles, fonctionnement et interactions (MTG)

Sakashima's Protege is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Flash Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.) You may have this creature enter as a copy of any permanent that entered this turn.

How it works : Sakashima's Protege

Original English text — Wizards of the Coast / Scryfall

#1June 18, 2021· Wizards of the Coast
The mana value of a split card is determined by the combined mana cost of its two halves. If cascade allows you to cast a split card, you may cast either half but not both halves.
No other card is named in this ruling.
#2June 18, 2021· Wizards of the Coast
Cascade triggers when you cast the spell, meaning that it resolves before that spell. If you end up casting the exiled card, it will go on the stack above the spell with cascade.
No other card is named in this ruling.
#3June 18, 2021· Wizards of the Coast
When the cascade ability resolves, you must exile cards. The only optional part of the ability is whether or not you cast the last card exiled.
No other card is named in this ruling.
#4June 18, 2021· Wizards of the Coast
If a spell with cascade is countered, the cascade ability will still resolve normally.
No other card is named in this ruling.
#5June 18, 2021· Wizards of the Coast
You exile the cards face up. All players will be able to see them.
No other card is named in this ruling.
#6June 18, 2021· Wizards of the Coast
If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, you must pay those to cast the card.
No other card is named in this ruling.
#7June 18, 2021· Wizards of the Coast
If the card has in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
No other card is named in this ruling.
#8June 18, 2021· Wizards of the Coast
Due to a 2021 rules change to cascade, not only do you stop exiling cards if you exile a nonland card with lesser mana value than the spell with cascade, but the resulting spell you cast must also have lesser mana value. Previously, in cases where a card's mana value differed from the resulting spell, such as with some modal double-faced cards or cards with an Adventure, you could cast a spell with a higher mana value than the exiled card.
No other card is named in this ruling.
#9June 18, 2021· Wizards of the Coast
A spell's mana value is determined only by its mana cost. Ignore any alternative costs, additional costs, cost increases, or cost reductions.
No other card is named in this ruling.
#10November 10, 2020· Wizards of the Coast
Sakashima's Protege copies exactly what was printed on the original permanent (unless that permanent is copying something else or is a token; see below). It doesn't copy whether that permanent is tapped or untapped, whether it has any counters on it or any Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on.
No other card is named in this ruling.
#11November 10, 2020· Wizards of the Coast
If Sakashima's Protege enters the battlefield as a copy of a planeswalker, it will enter with a number of loyalty counters on it equal to the loyalty printed in the lower right corner of the planeswalker. It won't copy the number of counters currently on that planeswalker.
No other card is named in this ruling.
#12November 10, 2020· Wizards of the Coast
If the chosen permanent is copying something else (for example, if the chosen permanent is another Sakashima's Protege), then Sakashima's Protege enters the battlefield as whatever the chosen permanent copied.
No other card is named in this ruling.
#13November 10, 2020· Wizards of the Coast
If the chosen permanent is a token, Sakashima's Protege copies the original characteristics of that token as stated by the effect that put that token onto the battlefield. Sakashima's Protege doesn't become a token in this case.
No other card is named in this ruling.
#14November 10, 2020· Wizards of the Coast
Any enters-the-battlefield abilities of the copied permanent will trigger when Sakashima's Protege enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the chosen permanent will also work.
No other card is named in this ruling.
#15November 10, 2020· Wizards of the Coast
If Sakashima's Protege somehow enters the battlefield at the same time as another creature, it can't become a copy of that creature. You may choose only a creature that's already on the battlefield and entered the battlefield this turn.
No other card is named in this ruling.
#16November 10, 2020· Wizards of the Coast
If you cast a permanent spell using the cascade ability of Sakashima's Protege, that permanent will be on the battlefield in time to be copied by Sakashima's Protege.
No other card is named in this ruling.