Sapphire Medallion

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

Kamiz, Obscura Oculus

Whenever you attack, target attacking creature can't be blocked this turn. It connives. Then choose another attacking creature with lesser power. That creature gains double strike until end of turn. (To have a creature connive, draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)

Jet Medallion

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

Pearl Medallion

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

Sol Ring

Command Tower

{T}: Add one mana of any color in your commander's color identity.