Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Dimir Signet

Izzet Signet

Gruul Signet

Island

Rakdos Signet

Boros Signet

Mountain

Simic Signet

Orzhov Signet

Plains

Command Tower

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

Forest

Azorius Signet

Golgari Signet

Selesnya Signet

Exotic Orchard

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

Kenrith, the Returned King

{R}: All creatures gain trample and haste until end of turn.
{1}{G}: Put a +1/+1 counter on target creature.
{2}{W}: Target player gains 5 life.
{3}{U}: Target player draws a card.
{4}{B}: Put target creature card from a graveyard onto the battlefield under its owner's control.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Composite Golem

Sacrifice Composite Golem: Add {W}{U}{B}{R}{G}.

Arcane Signet

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Swamp

Sol Ring

Crackdown Construct

Whenever you activate an ability of an artifact or creature that isn't a mana ability, Crackdown Construct gets +1/+1 until end of turn.