Put a defender counter on each creature.

Counter target spell. That spell's controller reveals their hand.

Instant and sorcery spells you cast cost {1} less to cast.
{2}{U}: Level 2
When this Class becomes level 2, you may return target instant or sorcery card from your graveyard to your hand.
{3}{U}: Level 3
Once each turn, when you cast an instant or sorcery spell, you may copy that spell. You may choose new targets for the copies.

Enchant creature
When Left to the Sea enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Choose one —
• Draw three cards.
• Return up to two target creatures to their owners' hands.

At the beginning of your end step, scry 1. Then if it's your first turn of the game or you discarded a card named Leystone of Depths this turn, draw a card.
Cycling {U}

Create a 2/2 blue Drake creature token with flying.
Whenever a creature you control enters, if it wandered, you may exile Lofty Frontiers from your graveyard. If you do, create a 2/2 blue Drake creature token with flying.

Put any number of target noncreature cards from your graveyard on top of your library in any order.
Draw a card, then exile Long-Lost Legacy.

Indulgence
When Lost in the Moment enters, draw a card then discard a card.
Whenever you indulge, each opponent mills four cards.

Create X blue Shrine enchantment tokens named Unmarked Shrine with “At the beginning of your upkeep, each opponent mills a card.”
{1}{U}, Exile Lost to Memory from your graveyard: Draw two cards. Activate only if an opponent has eight or more cards in their graveyard.

Put a +1/+1 counter on target creature. It gets +0/+2 until end of turn.

Sacrifice a Treasure: Put a loyalty counter on Marilye, Dreaming Big.
[+1]: Draw a card, then discard a card. If you discarded a nonland card this way, create a tapped Treasure token.
[–3]: Gain control of target artifact. It becomes a Treasure artifact, loses all other types, and loses all abilities except for activated mana abilities.
[–8]: Target opponent chooses a nonland permanent they control. You gain control of the rest.

Choose a number between 0 and 5. Counter up to one target spell unless its controller pays {X}, where X is the chosen number. Then mill five minus X cards. You may return a card milled this way to your hand.

Create two 1/1 blue Wizard creature tokens with prowess.

Target artifact or creature's owner puts it on the top or bottom of their library.
Flashback {5}{U}{U}

Return target creature or enchantment to its owner's hand. If that permanent's controller has eight or more cards in their graveyard, its owner puts it on the top or bottom of their library instead.

Tap up to two target creatures. Put a stun counter on each of them.

Gain control of target nonland permanent until end of turn. Untap it. Then you may pay {2}. If you do, gain control of that permanent until the end of your next turn.

Enchant creature
Enchanted creature has “Whenever this creature deals combat damage to a player or planeswalker, scry 1, then draw a card.”

Look at the top X cards of your library, where X is one plus the number of differently named lands you control. Put up to three of them into your hand and the rest on the bottom of your library in a random order.

Flash
When Omen of Deception enters, counter target spell unless its controller pays {2}.
{2}{U}, Sacrifice Omen of Deception: Scry 2.

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Ephara.
When you sacrifice Ordeal of Ephara, return up to two target nonland permanents to their owner's hand.

Counter target spell. That spell's controller reveals their hand. Choose any number of nonland cards from it. That player puts those cards on the bottom of their library in any order, then draws that many cards.

Choose up to three different kinds of counters on permanents you control. For each of those kinds, you may put a counter of that kind on a permanent you control that doesn't have one.
Draw a card.

Choose target nonland permanent you control and up to two target nonland permanents you don't control. Return those permanents to their owner's hands.