As an additional cost to cast this spell, sacrifice a creature or enchantment.
Flying
When this creature enters, each opponent sacrifices a creature of their choice, then sacrifices an enchantment of their choice.

Look at the top five cards of your library. You may reveal a permanent card with mana value 3 or less from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Corrupt — Each player exiles the top X cards of their library. You may cast a spell from among them with mana value X or less without paying its mana cost. If you control a permanent with greater mana value than this spell, you may cast up to two spells with mana value X or less from among them without paying their mana costs instead.

Choose one —
• Target opponent reveals their hand. You choose a nonland card from it and exile that card.
• Target opponent exiles a creature or enchantment they control.

Put target creature on top of its owner's library. Its controller surveils 1, then you surveil 1.

Abominable Avalanche deals 3 damage divided as you choose among one, two, or three targets.
At the beginning of your end step, if you've spent at least five mana to cast spells this turn, you may exile Abominable Avalanche from your graveyard. If you do, create a 3/3 green Yeti creature token with trample.

This spell costs {1} less to cast for each creature you control.
Trample
When this creature enters, you may discard a card. If you do, draw two cards.

Target opponent reveals their hand. You choose a nonland card with mana value 2 or less from it or a card from their graveyard. Exile that card.

Exile all artifacts, creatures, and enchantments. Each player's life total becomes equal to their starting life total.

Create two 1/1 blue Bird creature tokens with flying, then create a token that's a copy of a token you control.

Gain control of target creature with mana value less than or equal to your devotion to blue.

When Ace Tamer enters, look at the top six cards of your library. You may reveal a non-Human creature card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

When Adaptive Hydra enters, teach it your choice of haste, menace, or vigilance. Then repeat this process X times.

Trample
This creature gets +1/+0 for each counter among creatures you control.
{2}{R}{G}: Put a +1/+1 counter on this creature.

Target creature you control gets +4/+3 until end of turn.

Whenever you cast a noncreature spell, create a 1/1 blue Bird creature token with flying.
Flow — {10}{W}{U}: Draw cards equal to half the number of cards in your library, rounded up.

Ward {2}
If you would put one or more counters on a permanent or player, put three times as many of each of those kinds of counters on that permanent or player instead.

Flash
When Agent of Deception enters, counter target creature or planeswalker spell unless its controller pays {X}, where X is your devotion to blue.

Flying, deathtouch

Vigilance
Whenever another creature you control dies, return to your hand target enchantment card from your graveyard with lesser mana value.

Flying, vigilance
Other creatures you control are Armies in addition to their other types.
At the beginning of your end step, create a 0/0 white Army creature token, then put a +1/+1 counter on each Army you control.

Target player reveals their hand. You choose a nonland card from it or a card from their graveyard. Exile that card. You lose 1 life.

Trample
Whenever a creature you control attacks alone, put four +1/+1 counters on it.

Ward {2}
Whenever one or more nontoken creatures you control leave the battlefield without dying, create a 1/1 blue Ninja creature token with “This creature can't be blocked by creatures with greater power.”

Menace, lifelink
Whenever a tapped creature you control dies, draw a card.