Samut, the Driving Force

First strike, vigilance, haste
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.)
Other creatures you control get +X/+0, where X is your speed.
Noncreature spells you cast cost {X} less to cast, where X is your speed.

Point the Way

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.)
{3}{G}, Sacrifice this enchantment: Search your library for up to X basic land cards, where X is your speed. Put those cards onto the battlefield tapped, then shuffle.

Amonkhet Raceway

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.)
{T}: Add {C}.
Max speed — {T}: Target creature gains haste until end of turn.

Endrider Spikespitter

Reach
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.)
Max speed — At the beginning of your upkeep, exile the top card of your library. You may play that card this turn.

Nesting Bot

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 creature dies, create a 1/1 colorless Servo artifact creature token.
Max speed — This creature gets +1/+0.

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Leonin Surveyor

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.)
During your turn, this creature has first strike.
Max speed — {3}, Exile this card from your graveyard: Draw a card.

Perilous Snare

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 artifact enters, exile target nonland permanent an opponent controls until this artifact leaves the battlefield.
Max speed — {T}: Put a +1/+1 counter on target creature or Vehicle you control. Activate only as a sorcery.

Avishkar Raceway

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.)
{T}: Add {C}.
Max speed — {3}, {T}, Discard a card: Draw a card.

Racers' Scoreboard

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 artifact enters, draw two cards, then discard a card.
Max speed — Spells you cast cost {1} less to cast.

Burnout Bashtronaut

Menace
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.)
{2}: This creature gets +1/+0 until end of turn.
Max speed — This creature has double strike.

Sol Ring

Muraganda Raceway

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.)
{T}: Add {C}.
Max speed — {T}: Add {C}{C}.

Starting Column

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.)
{T}: Add one mana of any color.
Max speed — {T}, Sacrifice this artifact: Draw two cards, then discard a card.

Kickoff Celebrations

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, you may discard a card. If you do, draw two cards.
Max speed — Sacrifice this enchantment: Creatures and Vehicles you control gain haste until end of turn.

Endrider Catalyzer

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.)
Max speed — {T}: Add {R}{R}.