Sulfur Elemental

Flash (You may cast this spell any time you could cast an instant.)
Split second (As long as this spell is on the stack, players can’t cast spells or activate abilities that aren’t mana abilities.)
White creatures get +1/-1.

Celestial Crusader

Flash (You may cast this spell any time you could cast an instant.)
Split second (As long as this spell is on the stack, players can’t cast spells or activate abilities that aren’t mana abilities.)
Flying
Other white creatures get +1/+1.

Aether Web

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +1/+1, has reach, and can block creatures with shadow as though they didn’t have shadow. (Creatures with reach can block creatures with flying.)

Bogardan Hellkite

Flash
Flying
When Bogardan Hellkite enters the battlefield, it deals 5 damage divided as you choose among any number of targets.

Ophidian Eye

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

Scryb Ranger

Flash (You may cast this spell any time you could cast an instant.)
Flying, protection from blue
Return a Forest you control to its owner’s hand: Untap target creature. Activate this ability only once each turn.

Mystic Snake

Flash
When Mystic Snake enters the battlefield, counter target spell.

Havenwood Wurm

Flash (You may cast this spell any time you could cast an instant.)
Trample

Foriysian Interceptor

Flash (You may cast this spell any time you could cast an instant.)
Defender
Foriysian Interceptor can block an additional creature each combat.

Feebleness

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets -2/-1.

Temporal Isolation

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature has shadow. (It can block or be blocked by only creatures with shadow.)
Prevent all damage that would be dealt by enchanted creature.

Plated Pegasus

Flash (You may cast this spell any time you could cast an instant.)
Flying
If a spell would deal damage to a permanent or player, prevent 1 damage that spell would deal to that permanent or player.

Viashino Bladescout

Flash (You may cast this spell any time you could cast an instant.)
When Viashino Bladescout enters the battlefield, target creature gains first strike until end of turn.

Teferi, Mage of Zhalfir

Flash (You may cast this spell any time you could cast an instant.)
Creature cards you own that aren’t on the battlefield have flash.
Each opponent can cast spells only any time they could cast a sorcery.

Ashcoat Bear

Flash (You may cast this spell any time you could cast an instant.)

Crookclaw Transmuter

Flash (You may cast this spell any time you could cast an instant.)
Flying
When Crookclaw Transmuter enters the battlefield, switch target creature’s power and toughness until end of turn.

Drudge Reavers

Flash (You may cast this spell any time you could cast an instant.)
: Regenerate Drudge Reavers.

Bogardan Rager

Flash (You may cast this spell any time you could cast an instant.)
When Bogardan Rager enters the battlefield, target creature gets +4/+0 until end of turn.

Ghitu Firebreathing

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
: Enchanted creature gets +1/+0 until end of turn.
: Return Ghitu Firebreathing to its owner’s hand.

Voidmage Husher

Flash (You may cast this spell any time you could cast an instant.)
When Voidmage Husher enters the battlefield, counter target activated ability. (Mana abilities can’t be targeted.)
Whenever you cast a spell, you may return Voidmage Husher to its owner’s hand.

Plaxmanta

Flash
When Plaxmanta enters the battlefield, creatures you control gain shroud until end of turn. (They can’t be the targets of spells or abilities.)
When Plaxmanta enters the battlefield, sacrifice it unless was spent to cast it.

Grifter’s Blade

Flash
As Grifter’s Blade enters the battlefield, choose a creature you control it could be attached to. If you do, it enters the battlefield attached to that creature.
Equipped creature gets +1/+1.
Equip

Quick Sliver

Flash
Any player may cast Sliver spells as though they had flash.