Myr Battlesphere

When Myr Battlesphere enters, 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.

Foundry Inspector

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

Myr Enforcer

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