Fellwar Stone

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

Izzet Signet

This land enters tapped.
{T}: Add {B}.
{T}, Sacrifice this land: Add {U}{R}.

({T}: Add {B} or {R}.)
This land enters tapped unless you control two or more basic lands.

This land enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

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

{T}: Add one mana of any type that a land you control could produce.

({T}: Add {B} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

This land enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

When this land enters, you gain 1 life.
{T}: Add {C}.
{1}, {T}: Add {U}, {B}, or {R}.

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

This land enters tapped.
{T}: Add {U}, {B}, or {R}.

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

You have no maximum hand size.
{T}: Add {C}.

({T}: Add {U} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.