Fellwar Stone

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

Rin and Seri, Inseparable

Whenever you cast a Dog spell, create a 1/1 green Cat creature token.
Whenever you cast a Cat spell, create a 1/1 white Dog creature token.
{R}{G}{W}, {T}: Rin and Seri deals damage to any target equal to the number of Dogs you control. You gain life equal to the number of Cats you control.

Crib Swap

Changeling (This card is every creature type.)
Exile target creature. Its controller creates a 1/1 colorless Shapeshifter creature token with changeling.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Talisman of Unity

{T}: Add {C}.
{T}: Add {G} or {W}. This artifact deals 1 damage to you.

Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on this creature.

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.

Cryptolith Rite

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

Yoshimaru, Ever Faithful

Whenever another legendary permanent you control enters, put a +1/+1 counter on Yoshimaru.
Partner (You can have two commanders if both have partner.)

Jinnie Fay, Jetmir's Second

If you would create one or more tokens, you may instead create that many 2/2 green Cat creature tokens with haste or that many 3/1 green Dog creature tokens with vigilance.

Arahbo, the First Fang

Other Cats you control get +1/+1.
Whenever Arahbo or another nontoken Cat you control enters, create a 1/1 white Cat creature token.

Felidar Retreat

Landfall — Whenever a land you control enters, choose one —
• Create a 2/2 white Cat Beast creature token.
• Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.

Regal Caracal

Other Cats you control get +1/+1 and have lifelink. (Damage dealt by those creatures also causes you to gain that much life.)
When this creature enters, create two 1/1 white Cat creature tokens with lifelink.

Kodama's Reach

Intangible Virtue

Creature tokens you control get +1/+1 and have vigilance.

Firdoch Core

Changeling (This card is every creature type.)
{T}: Add one mana of any color.
{4}: This artifact becomes a 4/4 artifact creature until end of turn.

Divine Resilience

Kicker {2}{W} (You may pay an additional {2}{W} as you cast this spell.)
Target creature you control gains indestructible until end of turn. If this spell was kicked, instead any number of target creatures you control gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Helpful Hunter

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Bloodline Pretender

Changeling (This card is every creature type.)
As this creature enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on this creature.

Trade Route Envoy

When this creature enters, draw a card if you control a creature with a counter on it. If you don't draw a card this way, put a +1/+1 counter on this creature.