Slaughter the Strong

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Mechtitan Core

{5}, Exile this Vehicle and four other artifact creatures and/or Vehicles you control: Create Mechtitan, a legendary 10/10 Construct artifact creature token with flying, vigilance, trample, lifelink, and haste that's all colors. When that token leaves the battlefield, return all cards exiled with this Vehicle except this card to the battlefield tapped under their owners' control.
Crew 2

Foundry Inspector

Artifact spells you cast cost {1} less to cast.

Island

Hotshot Mechanic

This creature crews Vehicles as though its power were 2 greater.

Peacewalker Colossus

{1}{W}: Another target Vehicle you control becomes an artifact creature until end of turn.
Crew 4 (Tap any number of creatures you control with total power 4 or more: This Vehicle becomes an artifact creature until end of turn.)

Thundersteel Colossus

Trample, haste
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Razortide Bridge

This land enters tapped.
Indestructible
{T}: Add {W} or {U}.

Mobilizer Mech

Flying
Whenever this Vehicle becomes crewed, up to one other target Vehicle you control becomes an artifact creature until end of turn.
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)

Darksteel Citadel

Born to Drive

Enchant artifact or creature
As long as enchanted permanent is a creature, it gets +1/+1 for each creature and/or Vehicle you control.
Channel — {2}{W}, Discard this card: Create two 1/1 colorless Pilot creature tokens with "This token crews Vehicles as though its power were 2 greater."

Etherium Sculptor

Thoughtcast

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Draw two cards.

The Omenkeel

Whenever a Vehicle you control deals combat damage to a player, that player exiles that many cards from the top of their library. You may play lands from among those cards for as long as they remain exiled.
Crew 1

Cosima, God of the Voyage

At the beginning of your upkeep, you may exile Cosima. If you do, it gains "Whenever a land you control enters, if Cosima is exiled, you may put a voyage counter on it. If you don't, return Cosima to the battlefield with X +1/+1 counters on it and draw X cards, where X is the number of voyage counters on it."

Cosima, God of the Voyage // The Omenkeel

Disruption Protocol

As an additional cost to cast this spell, tap an untapped artifact you control or pay {1}.
Counter target spell.

Plains

Tezzeret, Betrayer of Flesh

The first activated ability of an artifact you activate each turn costs {2} less to activate.
+1: Draw two cards. Then discard two cards unless you discard an artifact card.
−2: Target artifact becomes an artifact creature. If it isn't a Vehicle, it has base power and toughness 4/4.
−6: You get an emblem with "Whenever an artifact you control becomes tapped, draw a card."

Prodigy's Prototype

Whenever one or more Vehicles you control attack, create a 1/1 colorless Pilot creature token with "This token crews Vehicles as though its power were 2 greater."
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Mech Hangar

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Pilot or Vehicle spell.
{3}, {T}: Target Vehicle becomes an artifact creature until end of turn.