ガスタルの略奪者

エンジン始動！
このクリーチャーが戦場に出たとき、対戦相手１人を対象とする。そのプレイヤーは自分の手札を公開する。あなたはその中からインスタントやソーサリーであるカード１枚を選ぶ。そのプレイヤーはそのカードを捨てる。
最高速度 — このクリーチャーは+１/+１の修整を受け威迫を持つ。

Gastal Raider

Start your engines!
When this creature enters, target opponent reveals their hand. You choose an instant or sorcery card from it. That player discards that card.
Max speed — This creature gets +1/+1 and has menace.

Aetherdrift

Start your engines
When this creature enters, target opponent reveals their hand. You choose an instant or sorcery card from it. That player discards that card.
Max speed — This creature gets +1/+1 and has menace.

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

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

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.

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.

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.

“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.