Recruit Instructor

Whenever one or more Mice you control attack, draft a card from Recruit Instructor's spellbook.
Valiant — Whenever Recruit Instructor becomes the target of a spell or ability you control for the first time each turn, create a 1/1 white Mouse creature token.

Alchemy: Bloomburrow

"My angel is the flint, and I am her steel."

Angelfire Ignition

Put two +1/+1 counters on target creature. It gains vigilance, trample, lifelink, indestructible, and haste until end of turn.
Flashback {2}{R}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

"My family was saved thanks to a single Boros soldier. It's why I joined the Legion. I will be the protector now."

Defiant Strike

Target creature gets +1/+0 until end of turn.
Draw a card.

"My faith is stronger than fang, claw, or mindless hunger."

Moment of Heroism

Target creature gets +2/+2 and gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

Might doesn't make right, but it does win the fight.

Unleash Fury

Double the power of target creature until end of turn.

Crumb and Get It

Gift a Food (You may promise an opponent a gift as you cast this spell. If you do, they create a Food token before its other effects. It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
Target creature you control gets +2/+2 until end of turn. If the gift was promised, that creature also gains indestructible until end of turn.

Gift a Food (You may promise an opponent a gift as you cast this spell. If you do, they create a Food token before its other effects. It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
Target creature you control gets +2/+2 until end of turn. If the gift was promised, that creature also gains indestructible until end of turn.

As he grasped the glowing feather, the lizard's heart soared, and the rest of him quickly followed.

Feather of Flight

Flash
Enchant creature
When Feather of Flight enters, draw a card.
Enchanted creature gets +1/+0 and has flying.

Flash
Enchant creature
When this Aura enters, draw a card.
Enchanted creature gets +1/+0 and has flying.

"You stole a child from its nest," Mabel accused. "The only calamity I see here is you."

Mabel's Mettle

Target creature gets +2/+2 until end of turn. Up to one other target creature gets +1/+1 until end of turn.

"Fear is unavoidable. You can run from it with your tail between your legs, or charge it head on with sword in hand. I prefer the latter."
—Rho, veteran hero

Might of the Meek

Target creature gains trample until end of turn. It also gets +1/+0 until end of turn if you control a Mouse.
Draw a card.

Dangers sharper than thorns can hide among flowers.

War Squeak

Enchant creature
When War Squeak enters, target creature an opponent controls can't block this turn.
Enchanted creature gets +1/+1 and has haste.

Enchant creature
When this Aura enters, target creature an opponent controls can't block this turn.
Enchanted creature gets +1/+1 and has haste.

"Get back here, vile rodent! I was almost done cursing that ring!"

Cheeky House-Mouse // Squeak By

Embercleave

Flash
This spell costs {1} less to cast for each attacking creature you control.
When Embercleave enters, attach it to target creature you control.
Equipped creature gets +1/+1 and has double strike and trample.
Equip {3}

Become Brutes

One or two target creatures each gain haste until end of turn. For each of those creatures, create a Monster Role token attached to it. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has trample.)

"Saving a stranger's life is an excellent recruitment method. Luckily, peril is so easy to come by."
—Falco Spara

Boon of Safety

Put a shield counter on target creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)
Scry 1.

The giant had heard of locks, but he had yet to discover a door he couldn't open.

Barge In

Target attacking creature gets +2/+2 until end of turn. Each attacking non-Human creature gains trample until end of turn.