Arcane Signet

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

Forest

Command Tower

Boros Signet

Mirror Gallery

Saskia the Unyielding

Vigilance, haste
As Saskia enters, choose a player.
Whenever a creature you control deals combat damage to a player, it deals that much damage to the chosen player.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.

Sol Ring

Rakdos Signet

Plains

Swamp

Gruul Signet

Mountain

Selesnya Signet

Orzhov Signet

Sower of Discord

Flying
As this creature enters, choose two players.
Whenever damage is dealt to one of the chosen players, the other chosen player also loses that much life.

Legion Loyalty

Creatures you control have myriad. (Whenever a creature with myriad attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

The Master, Multiplied

Myriad
The "legend rule" doesn't apply to creature tokens you control.
Triggered abilities you control can't cause you to sacrifice or exile creature tokens you control.

Golgari Signet

Commander's Sphere

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