Golgari Signet

Karador, Ghost Chieftain

This spell costs {1} less to cast for each creature card in your graveyard.
Once during each of your turns, you may cast a creature spell from your graveyard.

Selesnya Signet

Orzhov Signet

Arcane Signet

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

Sol Ring

Voice of Resurgence

Whenever an opponent casts a spell during your turn and when Voice of Resurgence dies, create a green and white Elemental creature token with "This creature's power and toughness are each equal to the number of creatures you control."