Dovin's Veto

This spell can't be countered.
Counter target noncreature spell.

Aviary Mechanic

When Aviary Mechanic enters, you may return another permanent you control to its owner's hand.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Omen of the Sea

Flash (You may cast this spell any time you could cast an instant.)
When Omen of the Sea enters, scry 2, then draw a card.
{2}{U}, Sacrifice Omen of the Sea: Scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Tranquil Cove

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {U}.

Mystical Dispute

This spell costs {2} less to cast if it targets a blue spell.
Counter target spell unless its controller pays {3}.

The Birth of Meletis

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Search your library for a basic Plains card, reveal it, put it into your hand, then shuffle.
II — Create a 0/4 colorless Wall artifact creature token with defender.
III — You gain 2 life.

Island

Reflector Mage

When Reflector Mage enters, return target creature an opponent controls to its owner's hand. That creature's owner can't cast spells with the same name as that creature until your next turn.

Thraben Inspector

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

Usher to Safety

Return target permanent you control to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Shepherd of the Flock

Shepherd of the Flock // Usher to Safety

Oketra's Monument

White creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, create a 1/1 white Warrior creature token with vigilance.

Censor

Counter target spell unless its controller pays {1}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Jeskai Barricade

Flash (You may cast this spell any time you could cast an instant.)
Defender
When Jeskai Barricade enters, you may return another target creature you control to its owner's hand.

Elite Guardmage

Flying
When Elite Guardmage enters, you gain 3 life and draw a card.

Azorius Guildgate

This land enters tapped.
{T}: Add {W} or {U}.

Plains

Rescuer Sphinx

Flying
As Rescuer Sphinx enters, you may return a nonland permanent you control to its owner's hand. If you do, Rescuer Sphinx enters with a +1/+1 counter on it.