Mycosynth Golem

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Artifact creature spells you cast have affinity for artifacts. (They cost {1} less to cast for each artifact you control.)

Secret Lair Drop

The List

Fifth Dawn

Affinity for artifacts (This spell costs {1} less to play for each artifact you control.)
Artifact creature spells you play have affinity for artifacts. (They cost {1} less to play for each artifact you control.)

If Mycosynth Golem is sacrificed as part of the cost to cast a spell, the cost reduction will already be locked in, and the cost won’t be increased.

The spells gain affinity for artifacts as they’re put onto the stack. They don’t have the ability while they’re cards in your hand.

Two or more instances of the affinity ability are cumulative, even if they’re both affinity for the same thing.