Keen Engineering

Sonic: Turbo Gear

Sonic: Turbo Gear Foil Edition

Mardu Surge

Creative Energy

Creative Energy Collector's Edition

Growing Threat

Rebellion Rising

Urza's Iron Alliance

Lorehold Legacies

Exquisite Invention

Built From Scratch

Ingenious Machinists

Invent Superiority

Eternal Bargain

Spiraling Doom

Scars of Mirrodin Foil Redemption

Scars of Mirrodin Redemption

Myr of Mirrodin

Myr Battlesphere

When this creature enters, create four 1/1 colorless Myr artifact creature tokens.
Whenever this creature attacks, you may tap X untapped Myr you control. If you do, this creature gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.

When Myr Battlesphere enters the battlefield, create four 1/1 colorless Myr artifact creature tokens.
Whenever Myr Battlesphere attacks, you may tap X untapped Myr you control. If you do, Myr Battlesphere gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.