Flash
When Omen of Victory enters, create a 0/0 white Army creature token, then put two +1/+1 counters on it.
{2}{W}, Sacrifice Omen of Victory: 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 Athreos.
When you sacrifice Ordeal of Athreos, return target creature card from your graveyard to the battlefield.

Exile target creature. Tap up to two other target creatures if the exiled creature had power 3 or less.

Each player who doesn't control a planeswalker can't cast more than one spell each turn.
Ayeshicycling {3}

Exile target creature you control, then return that card to the battlefield under its owner's control.

Each player who controls an artifact or enchantment creates a 2/2 white Mouse creature token. Then destroy all artifacts and enchantments.

Return up to one target artifact, enchantment, or land card from your graveyard to your hand.
Create two Berry tokens.

Enchant artifact, creature, or planeswalker
When you control a permanent with mana value greater than enchanted permanent's mana value, exile enchanted permanent.

Plasma Strike deals 3 damage to target attacking, blocking, or tapped creature.

Once each turn, when you activate a creature, you may create a tapped token that's a copy of it, except it's a 1/1 Toy in addition to its other types and it isn't legendary.

Whenever you gain life, you may create a 0/0 colorless Robot artifact creature token with X +1/+1 counters on it, where X is the amount of life you gained. Do this only once each turn.

Whenever you attack with exactly two creatures, draw a card. Prevent all damage that would be dealt to creatures you control this turn.

Whenever this Subroutine runs, return target creature card with mana value 3 or less from your graveyard to the battlefield.

Creatures you control get +2/+0 until end of turn.
If a nontoken creature you control would die this turn, cache it instead.

This spell has lifelink as long as you control a creature with lifelink.
Retaliatory Outburst deals 4 damage to target tapped creature.

Time loop
I, II — Look at the top six cards of your library. Put up to one nonland permanent card with mana value 3 or less from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
III — Creatures you control gain double strike until end of turn.

Choose one —
• Exile target artifact or enchantment.
• Exile target creature you control, then return it to the battlefield under its owner's control. If that creature entering the battlefield causes any abilities to trigger, those abilities trigger an additional time.

Target creature you control gets +2/+2 and gains indestructible until end of turn. If it was the target of another spell or ability this turn, create two 1/1 white Bird creature tokens with flying.

Flash
When Seal Away enters, exile target tapped creature an opponent controls until Seal Away leaves the battlefield.

When this enchantment enters, exile target nonland permanent an opponent controls until this enchantment leaves the battlefield.
Cycling {2}

Exile all creatures you don't control. Then return those cards to the battlefield tapped under their owners' control unless you've cast another spell named Second Crown's Fall this game. Then exile Second Crown's Fall.

At the beginning of your end step, put a +1/+1 counter on each tapped creature you control.
{G}{W}{U}, Remove five counters from among creatures you control, Sacrifice Severin's Masterwork: Create Chaneryx, Perfect Lifeform, a legendary 10/10 green, white, and blue Leviathan creature token with ward {10}.

At the beginning of your upkeep, create a 1/1 white Human creature token for each Shrine you control.

Exile target nonland permanent with mana value less than or equal to the amount of life you've lost this turn.

Exile target creature, then return that card to the battlefield under its owner's control. When you do, pay for and choose any number.
+{W} — Distribute two +1/+1 counters among one or two creatures you control.
+{C} — Exile that creature again. Return that card to the battlefield under its owner's control at the beginning of the next end step.
+{B} — All creatures get -1/-1 until end of turn.