Spirited Companion

When Spirited Companion enters, draw a card.

Celestial Unicorn

Whenever you gain life, put a +1/+1 counter on Celestial Unicorn.

Soul Warden

Whenever another creature enters, you gain 1 life.

Inspiring Overseer

Flying
When Inspiring Overseer enters, you gain 1 life and draw a card.

Thraben Inspector

When Thraben Inspector enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Benevolent Bodyguard

Sacrifice Benevolent Bodyguard: Target creature you control gains protection from the color of your choice until end of turn.

Triplicate Spirits

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.)
Create three 1/1 white Spirit creature tokens with flying. (They can't be blocked except by creatures with flying or reach.)

Battle Screech

Create two 1/1 white Bird creature tokens with flying.
Flashback—Tap three untapped white creatures you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Squadron Hawk

Flying
When Squadron Hawk enters, you may search your library for up to three cards named Squadron Hawk, reveal them, put them into your hand, then shuffle.

Plains

Rally the Peasants

Creatures you control get +2/+0 until end of turn.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Palace Sentinels

When Palace Sentinels enters, you become the monarch.

Boros Garrison

Boros Garrison enters tapped.
When Boros Garrison enters, return a land you control to its owner's hand.
{T}: Add {R}{W}.

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.

Prismatic Strands

Prevent all damage that sources of the color of your choice would deal this turn.
Flashback—Tap an untapped white creature you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)