Thoughtweft Trio

First strike, vigilance
Champion a Kithkin (When this enters, sacrifice it unless you exile another Kithkin you control. When this leaves the battlefield, that card returns to the battlefield.)
Thoughtweft Trio can block any number of creatures.

Oblivion Ring

When Oblivion Ring enters, exile another target nonland permanent.
When Oblivion Ring leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Knight of Meadowgrain

First strike
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Militia's Pride

Whenever a nontoken creature you control attacks, you may pay {W}. If you do, create a 1/1 white Kithkin Soldier creature token that's tapped and attacking.

Brigid, Hero of Kinsbaile

First strike
{T}: Brigid, Hero of Kinsbaile deals 2 damage to each attacking or blocking creature target player controls.

Cenn's Heir

Whenever Cenn's Heir attacks, it gets +1/+1 until end of turn for each other attacking Kithkin.

Ballyrush Banneret

Kithkin spells and Soldier spells you cast cost {1} less to cast.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Goldmeadow Stalwart

As an additional cost to cast this spell, reveal a Kithkin card from your hand or pay {3}.

Wizened Cenn

Other Kithkin creatures you control get +1/+1.

Kithkin Rabble

Vigilance
Kithkin Rabble's power and toughness are each equal to the number of white permanents you control.

Plains

Rustic Clachan

As Rustic Clachan enters, you may reveal a Kithkin card from your hand. If you don't, Rustic Clachan enters tapped.
{T}: Add {W}.
Reinforce 1—{1}{W} ({1}{W}, Discard this card: Put a +1/+1 counter on target creature.)

Kinsbaile Borderguard

Kinsbaile Borderguard enters with a +1/+1 counter on it for each other Kithkin you control.
When Kinsbaile Borderguard dies, create a 1/1 white Kithkin Soldier creature token for each counter on it.

Journey to Nowhere

When Journey to Nowhere enters, exile target creature.
When Journey to Nowhere leaves the battlefield, return the exiled card to the battlefield under its owner's control.