Watcher of the Spheres

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

Ornitharch

Flying
Tribute 2 (As this creature enters, an opponent of your choice may put two +1/+1 counters on it.)
When this creature enters, if tribute wasn't paid, create two 1/1 white Bird creature tokens with flying.

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.

Radiant Purge

Exile target multicolored creature or multicolored enchantment.

Griffin Guide

Enchant creature
Enchanted creature gets +2/+2 and has flying.
When enchanted creature dies, create a 2/2 white Griffin creature token with flying.

Embrose, Dean of Shadow

{T}: Put a +1/+1 counter on another target creature, then Embrose deals 2 damage to that creature.
Whenever a creature you control with a +1/+1 counter on it dies, draw a card.

Shaile, Dean of Radiance

Flying, vigilance
{T}: Put a +1/+1 counter on each creature that entered the battlefield under your control this turn.

Shaile, Dean of Radiance // Embrose, Dean of Shadow

Wing Shards

Target player sacrifices an attacking creature of their choice.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Plains

Teach by Example

({U/R} can be paid with either {U} or {R}.)
When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Prairie Stream

({T}: Add {W} or {U}.)
This land enters tapped unless you control two or more basic lands.

Warden of Evos Isle

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

Tranquil Cove

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {U}.

Donal, Herald of Wings

Whenever you cast a nonlegendary creature spell with flying, you may copy it, except the copy is a 1/1 Spirit in addition to its other types. Do this only once each turn. (The copy becomes a token.)

Emeria Angel

Flying
Landfall — Whenever a land you control enters, you may create a 1/1 white Bird creature token with flying.

Empyrean Eagle

Flying
Other creatures you control with flying get +1/+1.

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.

Silver Raven

Flying
When this creature enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Island

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.)

Wingmate Roc

Flying
Raid — When this creature enters, if you attacked this turn, create a 3/4 white Bird creature token with flying.
Whenever this creature attacks, you gain 1 life for each attacking creature.

Sejiri Refuge

Azorius Keyrune

{T}: Add {W} or {U}.
{W}{U}: This artifact becomes a 2/2 white and blue Bird artifact creature with flying until end of turn.