Aven Eternal

Flying
When Aven Eternal enters, amass Zombies 1. (Put a +1/+1 counter on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

Sea Gate

Sea Gate enters tapped.
As Sea Gate enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Vulpikeet

Mutate {2}{W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flying
Whenever this creature mutates, put a +1/+1 counter on it.

Island

Azorius Guildgate

This land enters tapped.
{T}: Add {W} or {U}.

Take Up the Shield

Put a +1/+1 counter on target creature. It gains lifelink and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Aerie Auxiliary

Flying
When Aerie Auxiliary enters, support 2. (Put a +1/+1 counter on each of up to two other target creatures.)

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Plains

Welkin Tern

Flying (This creature can't be blocked except by creatures with flying or reach.)
Welkin Tern can block only creatures with flying.

Colorful Feiyi Sparrow

Flying (This creature can't be blocked except by creatures with flying or reach.)

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Annul

Counter target artifact or enchantment spell.

Winged Words

This spell costs {1} less to cast if you control a creature with flying.
Draw two cards.

Now for Wrath, Now for Ruin!

Put a +1/+1 counter on each creature you control. They gain vigilance until end of turn. The Ring tempts you.

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.)

Airborne Aid

Draw a card for each Bird on the battlefield.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ravenform

Exile target artifact or creature. Its controller creates a 1/1 blue Bird creature token with flying.
Foretell {U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Cloudfin Raptor

Flying
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Razortide Bridge

Razortide Bridge enters tapped.
Indestructible
{T}: Add {W} or {U}.

Lofty Denial

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

Basilisk Gate

{T}: Add {C}.
{2}, {T}: Target creature gets +X/+X until end of turn, where X is the number of Gates you control. Activate only as a sorcery.