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.)

Crookclaw Transmuter

Flash
Flying
When Crookclaw Transmuter enters, switch target creature's power and toughness until end of turn.

Angelsong

Prevent all combat damage that would be dealt this turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Step Through

Return two target creatures to their owners' hands.
Wizardcycling {2} ({2}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Perch Protection

Gift an extra turn (You may promise an opponent a gift as you cast this spell. If you do, they take an extra turn after this one.)
Create four 2/2 blue Bird creature tokens with flying. If the gift was promised, all permanents you control phase out, and until your next turn, your life total can't change and you gain protection from everything.
Exile Perch Protection.

Island

Contentious Plan

Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Draw a card.

Echoing Deeps

You may have Echoing Deeps enter tapped as a copy of any land card in a graveyard, except it's a Cave in addition to its other types.
{T}: Add {C}.

Aven Wind Mage

Flying
Whenever you cast an instant or sorcery spell, Aven Wind Mage gets +1/+1 until end of turn.

Forsake the Worldly

Exile target artifact or enchantment.
Cycling {2} ({2}, Discard this card: Draw a card.)

Seaside Haven

{T}: Add {C}.
{W}{U}, {T}, Sacrifice a Bird: Draw a card.

Sage's Dousing

Counter target spell unless its controller pays {3}. If you control a Wizard, draw a card.

Kangee, Sky Warden

Flying, vigilance
Whenever Kangee, Sky Warden attacks, attacking creatures with flying get +2/+0 until end of turn.
Whenever Kangee blocks, blocking creatures with flying get +0/+2 until end of turn.

Wrath of God

Destroy all creatures. They can't be regenerated.

Clear

Destroy target enchantment.
Cycling {2} ({2}, Discard this card: Draw a card.)

Kangee, Aerie Keeper

Kicker {X}{2} (You may pay an additional {X}{2} as you cast this spell.)
Flying
When Kangee, Aerie Keeper enters, if it was kicked, put X feather counters on it.
Other Bird creatures get +1/+1 for each feather counter on Kangee, Aerie Keeper.

Murmuration

Birds you control get +1/+1 and have vigilance.
At the beginning of your end step, for each spell you've cast this turn, create a 1/2 blue Bird creature token with flying named Storm Crow.

Crookclaw Elder

Flying
Tap two untapped Birds you control: Draw a card.
Tap two untapped Wizards you control: Target creature gains flying until end of turn.

Azorius Signet

Raise the Palisade

Choose a creature type. Return all creatures that aren't of the chosen type to their owners' hands.

Ordered Migration

Domain — Create a 1/1 blue Bird creature token with flying for each basic land type among lands you control.

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.

Leech Bonder

Leech Bonder enters with two -1/-1 counters on it.
{U}, {Q}: Move a counter from target creature onto a second target creature. ({Q} is the untap symbol.)

Lilypad Village

{T}: Add {C}.
{T}: Add {U}. Spend this mana only to cast a creature spell.
{U}, {T}: Surveil 2. Activate only if a Bird, Frog, Otter, or Rat entered the battlefield under your control this turn.

Aven Wind Guide

Flying, vigilance
Creature tokens you control have flying and vigilance.
Embalm {4}{W}{U} ({4}{W}{U}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Bird Warrior with no mana cost. Embalm only as a sorcery.)

Zenith Seeker

Flying
Whenever you cycle or discard a card, target creature gains flying until end of turn.

Arctic Aven

Flying
Arctic Aven gets +1/+1 as long as you control a Plains.
{W}: Arctic Aven gains lifelink until end of turn. (Damage dealt by this creature also causes you to gain that much life.)

Nesting Grounds

{T}: Add {C}.
{1}, {T}: Move a counter from target permanent you control onto another target permanent. Activate only as a sorcery.

Stream of Unconsciousness

Target creature gets -4/-0 until end of turn. If you control a Wizard, draw a card.

Windcaller Aven

Flying
Cycling {U} ({U}, Discard this card: Draw a card.)
When you cycle Windcaller Aven, target creature gains flying until end of turn.

Watcher of the Spheres

Flying
Creature spells with flying you cast cost {1} less to cast.
Whenever another creature you control with flying enters, Watcher of the Spheres gets +1/+1 until end of turn.

Thespian's Stage

{T}: Add {C}.
{2}, {T}: Thespian's Stage becomes a copy of target land, except it has this ability.

Aven Windreader

Flying (This creature can't be blocked except by creatures with flying or reach.)
{1}{U}: Target player reveals the top card of their library.

Aven Fogbringer

Flying
When Aven Fogbringer enters, return target land to its owner's hand.

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Restless Anchorage

Restless Anchorage enters tapped.
{T}: Add {W} or {U}.
{1}{W}{U}: Until end of turn, Restless Anchorage becomes a 2/3 white and blue Bird creature with flying. It's still a land.
Whenever Restless Anchorage attacks, create a Map token.

Ash Barrens

{T}: Add {C}.
Basic landcycling {1} ({1}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Sage Aven

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Sage Aven enters, look at the top four cards of your library, then put them back in any order.

Copy Land

You may have Copy Land enter as a copy of any land on the battlefield, except it's an enchantment in addition to its other types.

Airborne Aid

Draw a card for each Bird on the battlefield.

Goldberry, River-Daughter

{T}: Move a counter of each kind not on Goldberry, River-Daughter from another target permanent you control onto Goldberry.
{U}, {T}: Move one or more counters from Goldberry onto another target permanent you control. If you do, draw a card.

Plains

Fleeting Aven

Flying
Whenever a player cycles a card, return Fleeting Aven to its owner's hand.

Steady Progress

Aven Augur

Flying
Sacrifice Aven Augur: Return up to two target creatures to their owners' hands. Activate only during your upkeep.

Reject Imperfection

Counter target spell. If that spell's mana value was 3 or less, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Vedalken Aethermage

Flash (You may cast this spell any time you could cast an instant.)
When Vedalken Aethermage enters, return target Sliver to its owner's hand.
Wizardcycling {3} ({3}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Migratory Route

Create four 1/1 white Bird creature tokens with flying.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Nimble Obstructionist

Flash
Flying
Cycling {2}{U} ({2}{U}, Discard this card: Draw a card.)
When you cycle Nimble Obstructionist, counter target activated or triggered ability you don't control.

Dazzling Denial

Counter target spell unless its controller pays {2}. If you control a Bird, counter that spell unless its controller pays {4} instead.

Archaeomancer's Map

When Archaeomancer's Map enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle.
Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.

Enlightened Tutor

Search your library for an artifact or enchantment card, reveal it, then shuffle and put that card on top.

The Raven's Warning

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Create a 1/1 blue Bird creature token with flying. You gain 2 life.
II — Whenever one or more creatures you control with flying deal combat damage to a player this turn, look at that player's hand and draw a card.
III — You may put a card you own from outside the game on top of your library.

Unbounded Potential

Choose one —
• Put a +1/+1 counter on each of up to two target creatures.
• Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Entwine {3}{W} (Choose both if you pay the entwine cost.)

Ripples of Potential

Proliferate, then choose any number of permanents you control that had a counter put on them this way. Those permanents phase out. (To proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there. Treat phased-out permanents and anything attached to them as though they don't exist until their controller's next turn.)

Vesuva

You may have Vesuva enter tapped as a copy of any land on the battlefield.

Resourceful Defense

Whenever a permanent you control leaves the battlefield, if it had counters on it, put those counters on target permanent you control.
{4}{W}: Move any number of counters from target permanent you control to another target permanent you control.

Reconnaissance Mission

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Akroma's Vengeance

Destroy all artifacts, creatures, and enchantments.
Cycling {3} ({3}, Discard this card: Draw a card.)

Gravitational Shift

Creatures with flying get +2/+0.
Creatures without flying get -2/-0.

Alrund's Epiphany

Create two 1/1 blue Bird creature tokens with flying. Take an extra turn after this one. Exile Alrund's Epiphany.
Foretell {4}{U}{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.)

Warden of Evos Isle

Flying
Creature spells with flying you cast cost {1} less to cast.

Soulcatchers' Aerie

Whenever a Bird is put into your graveyard from the battlefield, put a feather counter on Soulcatchers' Aerie.
Bird creatures get +1/+1 for each feather counter on Soulcatchers' Aerie.

Sol Ring

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Karn's Bastion

{T}: Add {C}.
{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Aerial Surveyor

Flying
Whenever Aerial Surveyor attacks, if defending player controls more lands than you, search your library for a basic Plains card, put it onto the battlefield tapped, then shuffle.
Crew 2

Tezzeret's Gambit

({U/P} can be paid with either {U} or 2 life.)
Draw two cards, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Aven Fateshaper

Flying
When Aven Fateshaper enters, look at the top four cards of your library, then put them back in any order.
{4}{U}: Look at the top four cards of your library, then put them back in any order.

Gust of Wind

This spell costs {2} less to cast if you control a creature with flying.
Return target nonland permanent you don't control to its owner's hand.
Draw a card.

Frost Trickster

Flying
When Frost Trickster enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Irrigated Farmland

({T}: Add {W} or {U}.)
Irrigated Farmland enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Crystalline Resonance

Whenever you cycle a card, you may have Crystalline Resonance become a copy of another target permanent until your next turn, except it has this ability.

Keeper of the Nine Gales

Flying
{T}, Tap two untapped Birds you control: Return target permanent to its owner's hand.

Aven Mimeomancer

Flying
At the beginning of your upkeep, you may put a feather counter on target creature. If you do, that creature has base power and toughness 3/1 and has flying for as long as it has a feather counter on it.

Aven Mindcensor

Flash
Flying
If an opponent would search a library, that player searches the top four cards of that library instead.

Curiosity Crafter

Flying
You have no maximum hand size.
Whenever a creature token you control deals combat damage to a player, draw a card.