Quicksilver Behemoth

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
When Quicksilver Behemoth attacks or blocks, return it to its owner's hand at end of combat. (Return it only if it's on the battlefield.)

Steelfin Whale

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Whenever an artifact you control enters, untap Steelfin Whale.

Myr Enforcer

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