Arcane Signet

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

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Double Major

Copy target creature spell you control, except it isn't legendary if the spell is legendary. (A copy of a creature spell becomes a token.)

Jackal, Genius Geneticist

Trample
Whenever you cast a creature spell with mana value equal to Jackal's power, copy that spell, except the copy isn't legendary. Then put a +1/+1 counter on Jackal. (The copy becomes a token.)

Hinterland Harbor

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

Mockingbird

Flying
You may have this creature enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast this creature, except it's a Bird in addition to its other types and it has flying.

Moxite Refinery

{2}, {T}, Remove X counters from an artifact or creature you control: Choose one. Activate only as a sorcery.
• Put X charge counters on target artifact.
• Put X +1/+1 counters on target creature.

Have

Goldberry, River-Daughter

{T}: Move a counter of each kind not on Goldberry from another target permanent you control onto Goldberry.
{U}, {T}: Move one or more counters from Goldberry onto another target permanent you control. If you do, draw a card.

Tatyova, Benthic Druid

Landfall — Whenever a land you control enters, you gain 1 life and draw a card.

Counterspell

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

Willowrush Verge

{T}: Add {U}.
{T}: Add {G}. Activate only if you control a Forest or an Island.

Command Tower

Negate

Dreamroot Cascade

This land enters tapped unless you control two or more other lands.
{T}: Add {G} or {U}.