Spells can't be countered.
Each instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost.

Convoke
Enchant creature
When this Aura enters, draw a card.
Enchanted creature gets +2/+2 and has flying.

Hexproof
Whenever this creature deals combat damage to a player, if you control no other creatures, look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Draw three cards.
Islandcycling

Counter target spell. Return target permanent to its owner's hand.

: Draw a card. Activate only during your turn, before attackers are declared.

Draw X cards, where X is the number of card types among cards in your graveyard.

, Sacrifice this creature: Each player exiles all cards from their hand face down and draws seven cards. At the beginning of the next end step, each player discards their hand and returns to their hand each card they exiled this way.

Flying, vigilance, ward
Whenever you commit a crime, surveil 2. This ability triggers only once each turn.

Flying
Whenever this creature deals combat damage to a player, choose a card in your hand. That player guesses whether the card's mana value is greater than 4. If the player guessed wrong, you may cast the card without paying its mana cost.

Flying
: This creature deals 1 damage to any target.

(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.)
When you unlock this door, draw three cards, then discard a card.

Flying
Whenever you cast a kicked spell, scry 2.

When this creature enters, create two 0/2 blue Illusion creature tokens with "Whenever this token blocks a creature, that creature doesn't untap during its controller's next untap step."
This creature has hexproof as long as you control an Illusion.

Flying
When this creature dies, draw a card.

Whenever you cast an instant or sorcery spell, create an X/X colorless Construct artifact creature token, where X is that spell's mana value.
, Exile this enchantment: Return all instant and sorcery cards from your graveyard to your hand. Activate only if you control six or more artifacts.

Enchant creature
You control enchanted creature.

Dominate Monster — When this creature enters, gain control of target creature for as long as you control this creature.

Flying
: This creature's owner shuffles it into their library. If that player does, they reveal cards from the top of that library until a card named Mirror-Mad Phantasm is revealed. The player puts that card onto the battlefield and all other cards revealed this way into their graveyard.

You may exile a blue card from your hand rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Permanents don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player chooses a permanent for each card in their graveyard, then untaps those permanents.

Flying
: This creature becomes the creature type of your choice until end of turn.
Morph

Flying
You may look at the top card of your library any time.
You may cast artifact spells from the top of your library.
Artifacts you control have ": Add . Spend this mana only to cast a spell from anywhere other than your hand."

: Untap this creature.
: This creature gains flying until end of turn.
: This creature gains shroud until end of turn.
: This creature gets +1/-1 until end of turn.
: This creature gets -1/+1 until end of turn.

Flying
Whenever another creature dies, you may draw a card. If you do, discard a card.

Choose three. You may choose the same mode more than once.
• Counter target spell unless its controller pays .
• Return target creature to its owner's hand.
• Draw a card.

Flying
Each other Merfolk you control with a +1/+1 counter on it has flying.
At the beginning of combat on your turn, target creature you control connives.

Enchant artifact or creature
Enchanted permanent doesn't untap during its controller's untap step.
At the beginning of the upkeep of enchanted permanent's controller, that player loses 1 life.

When Octo Opus enters, create a 4/4 blue Octopus Performer creature token named Contortionist with "At the beginning of your upkeep, you may fold this token in half." (It becomes 2/2, then 1/1, ½/½, and so on.)
Sacrifice Octo Opus: Draw a card and an additional card for each of Contortionist's folds.