Forest

Have

Gallant Fowlknight

When this creature enters, creatures you control get +1/+0 until end of turn. Kithkin creatures you control also gain first strike until end of turn.

Appeal to Eirdu

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
One or two target creatures each get +2/+1 until end of turn.

Mistmeadow Council

This spell costs {1} less to cast if you control a Kithkin.
When this creature enters, draw a card.

Getting

Eclipsed Kithkin

When this creature enters, look at the top four cards of your library. You may reveal a Kithkin, Forest, or Plains card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Kithkeeper

Vivid — When this creature enters, create X 1/1 green and white Kithkin creature tokens, where X is the number of colors among permanents you control.
Tap three untapped creatures you control: This creature gets +3/+0 and gains flying until end of turn.

Plains

Brigid, Doun's Mind

{T}: Add X {G} or X {W}, where X is the number of other creatures you control.
At the beginning of your first main phase, you may pay {W}. If you do, transform Brigid.

Brigid, Clachan's Heart

Whenever this creature enters or transforms into Brigid, Clachan's Heart, create a 1/1 green and white Kithkin creature token.
At the beginning of your first main phase, you may pay {G}. If you do, transform Brigid.

Brigid, Clachan's Heart // Brigid, Doun's Mind

Wary Farmer

At the beginning of your end step, if another creature entered the battlefield under your control this turn, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Crossroads Watcher

Trample
Whenever another creature you control enters, this creature gets +1/+0 until end of turn.

Kinbinding

Creatures you control get +X/+X, where X is the number of creatures that entered the battlefield under your control this turn.
At the beginning of combat on your turn, create a 1/1 green and white Kithkin creature token.

Bristlebane Outrider

This creature can't be blocked by creatures with power 2 or less.
As long as another creature entered the battlefield under your control this turn, this creature gets +2/+0.

Kinsbaile Aspirant

As an additional cost to cast this spell, behold a Kithkin or pay {2}. (To behold a Kithkin, choose a Kithkin you control or reveal a Kithkin card from your hand.)
Whenever another creature you control enters, this creature gets +1/+1 until end of turn.

Timid Shieldbearer

{4}{W}: Creatures you control get +1/+1 until end of turn.

Liminal Hold

When this enchantment enters, exile up to one target nonland permanent an opponent controls until this enchantment leaves the battlefield. You gain 2 life.

Thoughtweft Lieutenant

Whenever this creature or another Kithkin you control enters, target creature you control gets +1/+1 and gains trample until end of turn.

Thoughtweft Charge

Target creature gets +3/+3 until end of turn. If a creature entered the battlefield under your control this turn, draw a card.

Winnowing

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
For each player, you choose a creature that player controls. Then each player sacrifices all other creatures they control that don't share a creature type with the chosen creature they control.

Goldmeadow Nomad

{W}, Exile this card from your graveyard: Create a 1/1 green and white Kithkin creature token. Activate only as a sorcery.

Assert Perfection

Target creature you control gets +1/+0 until end of turn. It deals damage equal to its power to up to one target creature an opponent controls.

Rooftop Percher

Changeling (This card is every creature type.)
Flying
When this creature enters, exile up to two target cards from graveyards. You gain 3 life.

Blossoming Defense

Target creature you control gets +2/+2 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Figure of Fable

{G/W}: This creature becomes a Kithkin Scout with base power and toughness 2/3.
{1}{G/W}{G/W}: If this creature is a Scout, it becomes a Kithkin Soldier with base power and toughness 4/5.
{3}{G/W}{G/W}{G/W}: If this creature is a Soldier, it becomes a Kithkin Avatar with base power and toughness 7/8 and protection from each of your opponents.

Thoughtweft Imbuer

Whenever a creature you control attacks alone, it gets +X/+X until end of turn, where X is the number of Kithkin you control.

Surly Farrier

{T}: Target creature you control gets +1/+1 and gains vigilance until end of turn. Activate only as a sorcery.

Chomping Changeling

Changeling (This card is every creature type.)
When this creature enters, destroy up to one target artifact or enchantment.