Inherited Envelope

When Inherited Envelope enters, the Ring tempts you.
{T}: Add one mana of any color.

Commander's Sphere

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

Byode, Inverse Sun

+2: Mill three cards, then return any number of cards from different Universes milled this way from your graveyard to your hand.
-X: Choose a Universe you haven't chosen this way this game. You may cast a spell from that Universe with mana value X or less from your hand without paying its mana cost.
Byode, Inverse Sun can be your commander.
Your deck can include Universes Beyond cards of any color identity.

Biophagus

Genomic Enhancement — {T}: Add one mana of any color. If this mana is spent to cast a creature spell, that creature enters with an additional +1/+1 counter on it.

Arcane Signet

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

Fellwar Stone

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

Reclusive Taxidermist

Reclusive Taxidermist gets +3/+2 as long as there are four or more creature cards in your graveyard.
{T}: Add one mana of any color.