Tarkir: Dragonstorm Commander

Creature — Dragon

Flying, haste
You may exert this creature as it attacks. When you do, it deals 4 damage to target non-Dragon creature an opponent controls. (An exerted creature won't untap during your next untap step.)

Glorybringer

Aetherdrift Promos

Basri, Tomorrow's Champion

Legendary Creature — Human Knight

{W}, {T}, Exert Basri: Create a 1/1 white Cat creature token with lifelink. (An exerted creature won't untap during your next untap step.)
Cycling {2}{W} ({2}{W}, Discard this card: Draw a card.)
When you cycle this card, Cats you control gain hexproof and indestructible until end of turn.

Foundations Jumpstart

Copy

Creature — Minotaur Berserker Wizard

Trample
You may exert this creature as it attacks. When you do, create a tapped and attacking token that's a copy of target creature you control. Sacrifice the token at the beginning of the next end step. (An exerted creature won't untap during your next untap step.)

Sandstorm Crasher

Legendary Creature — Jackal Warrior

Trample
You may exert Anep as it attacks. When you do, exile the top two cards of your library. Until the end of your next turn, you may play those cards. (An exerted creature won't untap during your next untap step.)

Anep, Vizier of Hazoret

Creature — Minotaur Warrior

Haste (This creature can attack and {T} as soon as it comes under your control.)
You may exert this creature as it attacks. When you do, target creature can't block this turn. (An exerted creature won't untap during your next untap step.)

Ahn-Crop Crasher

Creature — Jackal Rogue

You may exert this creature as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, you may discard a card. If you do, draw a card.

Battlefield Scavenger

Creature — Human Warrior

If this creature hasn't been exerted this turn, you may exert it as it attacks. When you do, untap all other creatures you control and after this phase, there is an additional combat phase. (An exerted creature won't untap during your next untap step.)

Combat Celebrant

You may exert this creature as it attacks. When you do, it gets +1/+1 and gains menace until end of turn. (An exerted creature won't untap during your next untap step. A creature with menace can't be blocked except by two or more creatures.)

Emberhorn Minotaur

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
You may exert this creature as it attacks. When you do, it gets +1/+2 until end of turn. (An exerted creature won't untap during your next untap step.)

Nef-Crop Entangler

Creature — Jackal Warrior

You may exert this creature as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, creatures you control get +1/+0 until end of turn.

Trueheart Twins

Modern Horizons 3 Promos

Land

This land enters tapped unless you control a Mountain.
{T}: Add {R}.
{R}, {T}, Exert this land: Add {R}{R}. If any of that mana is spent on a creature spell, it gains haste until end of turn. (An exerted permanent won't untap during your next untap step.)

Arena of Glory

Modern Horizons 3

You may exert this creature as it attacks. When you do, target creature gets +X/+X until end of turn, where X is the number of counters on permanents you control. (An exerted creature won't untap during your next untap step.)
{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)

Hydra Trainer

Doctor Who

Artifact Creature — Robot

You may exert this creature as it attacks. When you do, it can't be blocked this turn and you scry 1. (An exerted creature won't untap during your next untap step. To scry 1, look at the top card of your library. You may put that card on the bottom.)

Clockwork Droid

Tales of Middle-earth Commander

Creature — Human Knight

You may exert this creature as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, reveal cards from the top of your library until you reveal an Equipment card. Put that card onto the battlefield attached to that creature, then put the rest on the bottom of your library in a random order.

Rohirrim Chargers

Universes Within

Legendary Creature — Dragon

Trample
When Themberchaud enters, he deals X damage to each other creature without flying and each player, where X is the number of Mountains you control.
You may exert Themberchaud as he attacks. When you do, he gains flying until end of turn. (An exerted creature won't untap during your next untap step.)

Themberchaud

The List

Creature — Human Wizard

You may exert this creature as it attacks. When you do, it gets +1/+1 and gains flying until end of turn. (An exerted creature won't untap during your next untap step.)

Gust Walker

You may exert this creature as it attacks. When you do, it gets +1/+0 and gains first strike until end of turn. (An exerted creature won't untap during your next untap step.)

Rhet-Crop Spearmaster

Menace
You may exert this creature as it attacks. When you do, it gets +2/+0 until end of turn. (An exerted creature won't untap during your next untap step.)

Khenra Scrapper

You may exert this creature as it attacks. When you do, it gets +1/+0 and gains deathtouch until end of turn. (An exerted creature won't untap during your next untap step.)

Bitterblade Warrior

Creature — Snake Warrior

You may exert this creature as it attacks. When you do, it gets +2/+2 until end of turn. (An exerted creature won't untap during your next untap step.)

Hooded Brawler

Hour of Devastation

Creature — Angel

Flying, vigilance
{2}{W}, {T}: Exile another target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.
{2}{W}, {T}, Exert this creature: Exile another target creature until this creature leaves the battlefield. (An exerted creature won't untap during your next untap step.)

Angel of Condemnation

You may exert this creature as it attacks. When you do, prevent all combat damage that would be dealt to it this turn. (An exerted creature won't untap during your next untap step.)

Oketra's Avenger

Warrior

{T}, Exert this creature: Create a 1/1 white Warrior creature token with vigilance. (An exerted creature won't untap during your next untap step.)

Steward of Solidarity

Creature — Human Cleric

You may exert this creature as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, tap target creature an opponent controls.

Vizier of the True

Hour of Devastation Promos

Creature — Cat

This creature gets +1/+1 for each other Cat you control.
{W}, {T}, Exert this creature: Create two 1/1 white Cat creature tokens with lifelink. (An exerted creature won't untap during your next untap step.)

Pride Sovereign

{T}: This creature deals 1 damage to target player or planeswalker.
{T}, Exert this creature: It deals 1 damage to target creature. (An exerted creature won't untap during your next untap step.)

Fervent Paincaster

Creature — Human Druid

{1}, {T}: Untap target land.
{1}, {T}, Exert this creature: Untap two target lands. (An exerted creature won't untap during your next untap step.)

Hope Tender

Creature — Snake Druid

{T}: Add one mana of any color.
{T}, Exert this creature: Add two mana of any one color. (An exerted creature won't untap during your next untap step.)

Oasis Ritualist

You may exert this creature as it attacks. When you do, it gets +1/+1 until end of turn and can't be blocked by creatures with power 2 or less this turn. (An exerted creature won't untap during your next untap step.)

Rhonas's Stalwart

You may exert this creature as it attacks. (It won't untap during your next untap step.)
Whenever you exert a creature, this creature deals 1 damage to each opponent and you gain 1 life.

Resolute Survivors

Amonkhet Promos

You may exert this creature as it attacks. When you do, it gets +1/+3 and gains lifelink until end of turn. (An exerted creature won't untap during your next untap step.)

Glory-Bound Initiate

Amonkhet

You may exert this creature as it attacks. When you do, return target creature card with mana value 2 or less from your graveyard to the battlefield. (An exerted creature won't untap during your next untap step.)

Devoted Crop-Mate

Creature — Bird Warrior

Flying
You may exert this creature as it attacks. When you do, creatures you control get +1/+1 until end of turn. (An exerted creature won't untap during your next untap step.)

Tah-Crop Elite

You may exert this creature as it attacks. When you do, you may put a creature card from your hand onto the battlefield. (An exerted creature won't untap during your next untap step.)

Champion of Rhonas

Creature — Snake Wizard

You may exert this creature as it attacks. When you do, draw a card. (An exerted creature won't untap during your next untap step.)

Watchful Naga

You may exert this creature as it attacks. When you do, untap all other creatures you control. (An exerted creature won't untap during your next untap step.)