Persistent Petitioners

{1}, {T}: Target player mills a card. (They put the top card of their library into their graveyard.)
Tap four untapped Advisors you control: Target player mills twelve cards.
A deck can have any number of cards named Persistent Petitioners.

Benefactor's Draught

Untap all creatures. Until end of turn, whenever a creature an opponent controls blocks, draw a card.
Draw a card.

Catalyst Stone

Flashback costs you pay cost {2} less.
Flashback costs your opponents pay cost {2} more.

To Arms!

Untap all creatures you control.
Draw a card.

Case of the Ransacked Lab

Instant and sorcery spells you cast cost {1} less to cast.
To solve — You've cast four or more instant and sorcery spells this turn. (If unsolved, solve at the beginning of your end step.)
Solved — Whenever you cast an instant or sorcery spell, draw a card.

Rustler Rampage

Spree (Choose one or more additional costs.)
+ {1} — Untap all creatures target player controls.
+ {1} — Target creature gains double strike until end of turn.

Roar of the Kha

Choose one —
• Creatures you control get +1/+1 until end of turn.
• Untap all creatures you control.
Entwine {1}{W} (Choose both if you pay the entwine cost.)

Aven Shrine

Whenever a player casts a spell, that player gains X life, where X is the number of cards in all graveyards with the same name as that spell.

Slime Against Humanity

Create a 0/0 green Ooze creature token with trample. Put X +1/+1 counters on it, where X is two plus the total number of cards you own in exile and in your graveyard that are Oozes or are named Slime Against Humanity.
A deck can have any number of cards named Slime Against Humanity.

Sol Ring

Council of the Absolute

As this creature enters, choose a noncreature, nonland card name.
Your opponents can't cast spells with the chosen name.
Spells with the chosen name you cast cost {2} less to cast.

Vitalize

Doc Aurlock, Grizzled Genius

Spells you cast from your graveyard or from exile cost {2} less to cast.
Plotting cards from your hand costs {2} less.

Mobilize

Katilda and Lier

Whenever you cast a Human spell, target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Kellan, the Kid

Flying, lifelink
Whenever you cast a spell from anywhere other than your hand, you may cast a permanent spell with equal or lesser mana value from your hand without paying its mana cost. If you don't, you may put a land card from your hand onto the battlefield.

Rally of Wings

Untap all creatures you control. Creatures you control with flying get +2/+2 until end of turn.

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Rally the Troops

Cast this spell only during the declare attackers step and only if you've been attacked this step.
Untap all creatures you control.

Prop Room

Untap each creature you control during each other player's untap step.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Dazzling Theater

Creature spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting a creature spell pays for {1} or one mana of that creature's color.)
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Dazzling Theater // Prop Room

Locket of Yesterdays

Spells you cast cost {1} less to cast for each card with the same name as that spell in your graveyard.

Riftstone Portal

{T}: Add {C}.
As long as this card is in your graveyard, lands you control have "{T}: Add {G} or {W}."

Call to Glory

Untap all creatures you control. Samurai creatures you control get +1/+1 until end of turn.