Arcane Signet

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

Dimir Signet

Ripples of Undeath

At the beginning of your first main phase, mill three cards. Then you may pay {1} and 3 life. If you do, put a card from among those cards into your hand.

Azorius Signet

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

The Master of Keys

Flying
When The Master of Keys enters, put X +1/+1 counters on it and mill twice X cards.
Each enchantment card in your graveyard has escape. The escape cost is equal to the card's mana cost plus exile three other cards from your graveyard. (You may cast cards from your graveyard for their escape cost.)