Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Seat of the Synod

Glacian, Powerstone Engineer

{T}, Tap X untapped artifacts you control: Look at the top X cards of your library. Put one of those cards into your hand and the rest into your graveyard.
Partner (You can have two commanders if both have partner.)

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.

Etherium Sculptor

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

Argivian Avenger

{1}: Until end of turn, Argivian Avenger gets -1/-1 and gains your choice of flying, vigilance, deathtouch, or haste.

Thoughtcast

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

Foundry Inspector

Myr Enforcer

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

Trusty Packbeast

When Trusty Packbeast enters, return target artifact card from your graveyard to your hand.

Argivian Restoration

Return target artifact card from your graveyard to the battlefield.

Rebbec, Architect of Ascension

Artifacts you control have protection from each mana value among artifacts you control.
Partner (You can have two commanders if both have partner.)

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Sojourner's Companion

Affinity for artifacts
Artifact landcycling {2} ({2}, Discard this card: Search your library for an artifact land card, reveal it, put it into your hand, then shuffle.)

Fall from Favor

Enchant creature
When Fall from Favor enters, tap enchanted creature and you become the monarch.
Enchanted creature doesn't untap during its controller's untap step unless that player is the monarch.