Momentum Breaker — ruling 1

Start your engines! isn’t a triggered ability. Increasing your speed to 1 is something that happens as a state-based action as soon as you control a permanent with the ability. Notably, this includes gaining control of a permanent with the ability that another player controls.

Momentum Breaker — ruling 2

Your speed doesn’t change until a spell or ability says so, such as the inherent triggered ability that cares about opponents losing life during your turn. Notably, losing control of permanents with start your engines! doesn’t affect your speed.

Momentum Breaker — ruling 3

Each player tracks their speed (or lack thereof) separately. Increasing your speed has no effect on whether another player has speed.

Momentum Breaker — ruling 4

If an effect needs to know what a player’s speed is and that player doesn’t have a speed, their speed is considered 0.

Momentum Breaker — ruling 5

A player “has max speed” if their speed is 4.

Momentum Breaker — ruling 6

“Max speed — [ability]” means “As long as you have max speed, this object has [ability].” If the granted ability functions in a zone other than the battlefield, the max speed ability does too.

Momentum Breaker : règles, fonctionnement et interactions (MTG)

Momentum Breaker 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

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.) When this enchantment enters, each opponent sacrifices a creature or Vehicle of their choice. Each opponent who can't discards a card. , Sacrifice this enchantment: You gain life equal to your speed.

Complete guide

Momentum Breaker is a versatile enchantment that brings the high-octane 'Start your engines!' mechanic to your games. It serves as both early-game disruption and late-game stabilization, forcing your opponents to lose resources while rewarding your aggressive playstyle. With the ability to cash in your speed for life, it ensures you can survive the very race you started.

Starting Your Engines

As soon as Momentum Breaker enters the battlefield, if you have no speed, your speed becomes 1 as a state-based action. This mechanic represents your progress in the race; once you have speed, it increases by 1 (up to a maximum of 4) the first time an opponent loses life during each of your turns. Importantly, even if Momentum Breaker leaves the battlefield, you retain your current speed level, as it is tracked separately for each player.

Resolution Step-by-Step

When you cast Momentum Breaker, its enter-the-battlefield ability triggers. First, each opponent must choose a creature or a Vehicle they control and sacrifice it. Only if an opponent controls no creatures and no Vehicles do they instead discard a card. This check is done individually for each opponent. Later, you can pay two mana and sacrifice the enchantment to gain life equal to your current speed, which provides a flexible way to recover after being pressured.

Common Pitfalls

A common mistake is thinking your speed resets to zero if your permanents with 'Start your engines!' are destroyed. Once you have a speed, it stays at that value unless an effect increases it or resets it. Additionally, remember that the speed increase only triggers on your turn when an opponent loses life; dealing damage to opponents on their turns will not rev your engine further.

When to Play Momentum Breaker

This card is best deployed when you can capitalize on its sacrifice effect to clear the way for your attackers. Because your speed increases when opponents lose life, it pairs perfectly with aggressive strategies or persistent life-loss effects. If your life total gets low, wait until your speed is at the maximum of 4 before sacrificing it to get the highest possible life gain.

Interaction examples

Setting the Pace

You cast Momentum Breaker while your speed is 0. As it enters, your speed immediately becomes 1. Your opponent is forced to sacrifice their only creature. If you later deal damage to them on your turn, your speed will increase to 2.

A Lack of Targets

If you play Momentum Breaker and your opponent has an empty board with no creatures or Vehicles, the sacrifice condition cannot be met. In this case, that opponent must discard a card from their hand instead.

Engines and Arenas

Phyrexian Arena

Note that Phyrexian Arena causes YOU to lose life during your upkeep. This does not increase your speed, as the 'Start your engines!' mechanic specifically requires an opponent to lose life during your turn to trigger the speed increase.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Momentum Breaker

Original English text — Wizards of the Coast / Scryfall

#1February 7, 2025· Wizards of the Coast
Start your engines! isn’t a triggered ability. Increasing your speed to 1 is something that happens as a state-based action as soon as you control a permanent with the ability. Notably, this includes gaining control of a permanent with the ability that another player controls.
No other card is named in this ruling.
#2February 7, 2025· Wizards of the Coast
Your speed doesn’t change until a spell or ability says so, such as the inherent triggered ability that cares about opponents losing life during your turn. Notably, losing control of permanents with start your engines! doesn’t affect your speed.
No other card is named in this ruling.
#3February 7, 2025· Wizards of the Coast
Each player tracks their speed (or lack thereof) separately. Increasing your speed has no effect on whether another player has speed.
No other card is named in this ruling.
#4February 7, 2025· Wizards of the Coast
If an effect needs to know what a player’s speed is and that player doesn’t have a speed, their speed is considered 0.
No other card is named in this ruling.
#5February 7, 2025· Wizards of the Coast
A player “has max speed” if their speed is 4.
No other card is named in this ruling.
#6February 7, 2025· Wizards of the Coast
“Max speed — [ability]” means “As long as you have max speed, this object has [ability].” If the granted ability functions in a zone other than the battlefield, the max speed ability does too.
No other card is named in this ruling.