Contentious Plan

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Sage's Nouliths

Job select (When this Equipment enters, create a 1/1 colorless Hero creature token, then attach this to it.)
Equipped creature gets +1/+0, has "Whenever this creature attacks, untap target attacking creature," and is a Cleric in addition to its other types.
Hagneia — Equip {3}

Chilling Chronicle

{1}, {T}: Tap target nonland permanent. Transform this artifact.

Mysterious Tome

{2}, {T}: Draw a card. Transform this artifact.

Mysterious Tome // Chilling Chronicle

Negate

Utrom Scientists

When this creature enters, tap up to one target creature and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Ultimecia, Temporal Threat

When Ultimecia enters, tap all creatures your opponents control.
Whenever a creature you control deals combat damage to a player, draw a card.

Crashing Wave

As an additional cost to cast this spell, waterbend {X}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)
Tap up to X target creatures, then distribute three stun counters among any number of tapped creatures your opponents control. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Overture

Target opponent mills half their library, rounded down. (Then exile this card. You may play the land later from exile.)

Jidoor, Aristocratic Capital

Jidoor, Aristocratic Capital // Overture

Unstoppable Plan

At the beginning of your end step, untap all nonland permanents you control.

Charmed Sleep

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Spectral Interference

Counter target artifact or creature spell unless its controller pays {4}.

Skimming Strike

Tap up to one target creature. Draw a card. (Then shuffle this card into its owner's library.)

Dirgur Island Dragon

Flying
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Dirgur Island Dragon // Skimming Strike

Tasha's Hideous Laughter

Each opponent exiles cards from the top of their library until that player has exiled cards with total mana value 20 or greater.

Stay Hidden, Stay Silent

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.
{4}{U}{U}: Shuffle enchanted creature into its owner's library, then manifest dread. Activate only as a sorcery.

Flood the Engine

Enchant creature or Vehicle
When this Aura enters, tap enchanted permanent.
Enchanted permanent loses all abilities and doesn't untap during its controller's untap step.

Dreams of Laguna

Surveil 1, then draw a card. (To surveil 1, look at the top card of your library. You may put it into your graveyard.)
Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tamiyo's Compleation

Flash
Enchant artifact, creature, or planeswalker
When this Aura enters, tap enchanted permanent. If it's an Equipment, unattach it.
Enchanted permanent loses all abilities and doesn't untap during its controller's untap step.

Ice Flan

When this creature enters, tap target artifact or creature an opponent controls. Put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Islandcycling {2} ({2}, Discard this card: Search your library for an Island card, reveal it, put it into your hand, then shuffle.)

Deflection

Change the target of target spell with a single target.

High Fae Trickster

Flash (You may cast this spell any time you could cast an instant.)
Flying
You may cast spells as though they had flash.

Sleep Magic

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.
When enchanted creature is dealt damage, sacrifice this Aura.

Cryogen Relic

When this artifact enters or leaves the battlefield, draw a card.
{1}{U}, Sacrifice this artifact: Put a stun counter on up to one target tapped creature. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Mechanozoa

When this creature enters, tap target artifact or creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Warp {2}{U} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Stuck in Summoner's Sanctum

Flash
Enchant artifact or creature
When this Aura enters, tap enchanted permanent.
Enchanted permanent doesn't untap during its controller's untap step and its activated abilities can't be activated.

Island

Leaden Fists

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +3/+3 and doesn't untap during its controller's untap step.

Mjölnir, Storm Hammer

When Mjölnir enters, attach it to target legendary creature you control.
Whenever equipped creature attacks, tap target creature defending player controls and put a stun counter on it. Then Mjölnir deals damage to each opponent equal to the number of tapped creatures that opponent controls.
Equip {4}

Thousand Winds

Flying
Morph {5}{U}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When this creature is turned face up, return all other tapped creatures to their owners' hands.

Magic Damper

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it.

Fuel for the Cause

Counter target spell, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Impede Momentum

Tap target creature and put three stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Ultros, Obnoxious Octopus

Whenever you cast a noncreature spell, if at least four mana was spent to cast it, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Whenever you cast a noncreature spell, if at least eight mana was spent to cast it, put eight +1/+1 counters on Ultros.

Rowdy Snowballers

When this creature enters, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Frost Breath

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

The Water Crystal

Blue spells you cast cost {1} less to cast.
If an opponent would mill one or more cards, they mill that many cards plus four instead.
{4}{U}{U}, {T}: Each opponent mills cards equal to the number of cards in your hand.

Juvenile Mist Dragon

Flying
Confounding Clouds — When this creature enters, for each opponent, tap up to one target creature that player controls. Each of those creatures doesn't untap during its controller's next untap step.

Relm's Sketching

Create a token that's a copy of target artifact, creature, or land.

Blustersquall

Tap target creature you don't control.
Overload {3}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Summon: Shiva

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Heavenly Strike — Tap target creature an opponent controls. Put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
III — Diamond Dust — Draw a card for each tapped creature your opponents control.

Stall Out

Tap target creature or Vehicle, then put three stun counters on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)
Cycling {2} ({2}, Discard this card: Draw a card.)

Harrier Strix

Flying
When this creature enters, tap target permanent.
{2}{U}: Draw a card, then discard a card.