Sol Ring

Arcane Signet

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

Forest

Fellwar Stone

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

Otrimi, the Ever-Playful

Mutate {1}{B}{G}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Trample
Whenever this creature deals combat damage to a player, return target creature card with mutate from your graveyard to your hand.