Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Passwall Adept

{2}{U}: Target creature can't be blocked this turn.

Sinister Sabotage

Counter target spell.
Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Artificer's Assistant

Flying
Whenever you cast a historic spell, scry 1. (Artifacts, legendaries, and Sagas are historic. To scry 1, look at the top card of your library, then you may put that card on the bottom.)

Omenspeaker

When Omenspeaker enters, 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.)

Thoughtbound Phantasm

Defender
Whenever you surveil, put a +1/+1 counter on Thoughtbound Phantasm.
As long as Thoughtbound Phantasm has three or more +1/+1 counters on it, it can attack as though it didn't have defender.

Amulet of Safekeeping

Whenever you become the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.
Creature tokens get -1/-0.

Cancel

Hornswoggle

Counter target creature spell. You create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Blink of an Eye

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
Return target nonland permanent to its owner's hand. If this spell was kicked, draw a card.

Negate

Academy Drake

Kicker {4} (You may pay an additional {4} as you cast this spell.)
Flying
If Academy Drake was kicked, it enters with two +1/+1 counters on it.

Mist-Cloaked Herald

Diamond Mare

As Diamond Mare enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Unwind

Counter target noncreature spell. Untap up to three lands.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Island

Magistrate's Scepter

{4}, {T}: Put a charge counter on Magistrate's Scepter.
{T}, Remove three charge counters from Magistrate's Scepter: Take an extra turn after this one.

Gearsmith Prodigy

Gearsmith Prodigy gets +1/+0 as long as you control an artifact.

Bone to Ash

Counter target creature spell.
Draw a card.

Muse Drake

Flying
When Muse Drake enters, draw a card.

Fleet Swallower

Whenever Fleet Swallower attacks, target player mills half their library, rounded up.

Syncopate

Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Nezahal, Primal Tide

This spell can't be countered.
You have no maximum hand size.
Whenever an opponent casts a noncreature spell, draw a card.
Discard three cards: Exile Nezahal, Primal Tide. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Essence Scatter

Time of Ice

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Tap target creature an opponent controls. It doesn't untap during its controller's untap step for as long as you control Time of Ice.
III — Return all tapped creatures to their owners' hands.