Syr Faren, the Hengehammer

Whenever Syr Faren attacks, another target attacking creature gets +X/+X until end of turn, where X is Syr Faren's power.

Gruul Beastmaster

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Whenever this creature attacks, another target creature you control gets +X/+0 until end of turn, where X is this creature's power.

Grotag Bug-Catcher

Trample
Whenever this creature attacks, it gets +1/+0 until end of turn for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Pathbreaker Ibex

Whenever this creature attacks, creatures you control gain trample and get +X/+X until end of turn, where X is the greatest power among creatures you control.

Lightning Runner

Double strike, haste
Whenever this creature attacks, you get {E}{E} (two energy counters), then you may pay eight {E}. If you pay, untap all creatures you control, and after this phase, there is an additional combat phase.

Tyrant's Familiar

Flying, haste
Lieutenant — As long as you control your commander, this creature gets +2/+2 and has "Whenever this creature attacks, it deals 7 damage to target creature defending player controls."

Drakuseth, Maw of Flames

Flying
Whenever Drakuseth attacks, it deals 4 damage to any target and 3 damage to each of up to two other targets.

Hellrider

Haste
Whenever a creature you control attacks, this creature deals 1 damage to the player or planeswalker it's attacking.

Tuya Bearclaw

Whenever Tuya Bearclaw attacks, it gets +X/+X until end of turn, where X is the greatest power among other creatures you control.

Impetuous Protege

Partner with Proud Mentor (When this creature enters, target player may put Proud Mentor into their hand from their library, then shuffle.)
Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the greatest power among tapped creatures your opponents control.

Xantid Swarm

Flying
Whenever this creature attacks, defending player can't cast spells this turn.

Terra Ravager

Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the number of lands defending player controls.

Slumbering Dragon

Flying
This creature can't attack or block unless it has five or more +1/+1 counters on it.
Whenever a creature attacks you or a planeswalker you control, put a +1/+1 counter on this creature.

Cultivator of Blades

Fabricate 2 (When this creature enters, put two +1/+1 counters on it or create two 1/1 colorless Servo artifact creature tokens.)
Whenever this creature attacks, you may have other attacking creatures get +X/+X until end of turn, where X is this creature's power.

Patron of the Akki

Goblin offering (You may cast this spell any time you could cast an instant by sacrificing a Goblin and paying the difference in mana costs between this and the sacrificed Goblin. Mana cost includes color.)
Whenever Patron of the Akki attacks, creatures you control get +2/+0 until end of turn.

Wild Beastmaster

Whenever this creature attacks, each other creature you control gets +X/+X until end of turn, where X is this creature's power.

Fangren Firstborn

Whenever this creature attacks, put a +1/+1 counter on each attacking creature.

Rubblebelt Rioters

Haste
Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the greatest power among creatures you control.

Hero of Oxid Ridge

Haste
Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
Whenever this creature attacks, creatures with power 1 or less can't block this turn.

Rubblebelt Raiders

Whenever this creature attacks, put a +1/+1 counter on it for each attacking creature you control.

Legion Warboss

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, create a 1/1 red Goblin creature token. That token gains haste until end of turn and attacks this combat if able.

Embereth Skyblazer

During your turn, this creature has flying.
Whenever this creature attacks, you may pay {2}{R}. If you do, creatures you control get +X/+0 until end of turn, where X is the number of opponents you have.

Hamlet Captain

Whenever this creature attacks or blocks, other Humans you control get +1/+1 until end of turn.

Myr Battlesphere

When this creature enters, create four 1/1 colorless Myr artifact creature tokens.
Whenever this creature attacks, you may tap X untapped Myr you control. If you do, this creature gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.

Rampaging Brontodon

Trample
Whenever this creature attacks, it gets +1/+1 until end of turn for each land you control.

Márton Stromgald

Whenever Márton Stromgald attacks, other attacking creatures get +1/+1 until end of turn for each attacking creature other than Márton Stromgald.
Whenever Márton Stromgald blocks, other blocking creatures get +1/+1 until end of turn for each blocking creature other than Márton Stromgald.

Inferno Titan

{R}: This creature gets +1/+0 until end of turn.
Whenever this creature enters or attacks, it deals 3 damage divided as you choose among one, two, or three targets.

Nacatl War-Pride

This creature must be blocked by exactly one creature if able.
Whenever this creature attacks, create X tokens that are copies of it and that are tapped and attacking, where X is the number of creatures defending player controls. Exile the tokens at the beginning of the next end step.

Goblin Wardriver

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)

Exuberant Wolfbear

Whenever this creature attacks, you may change the base power and toughness of target Human you control to this creature's power and toughness until end of turn.

Aurora of Emrakul

Flying, deathtouch
Whenever this creature attacks, each opponent loses 3 life.

Cryptolith Fragment

This artifact enters tapped.
{T}: Add one mana of any color. Each player loses 1 life.
At the beginning of your upkeep, if each player has 10 or less life, transform this artifact.

Cryptolith Fragment // Aurora of Emrakul

Aetherwind Basker

Trample
Whenever this creature enters or attacks, you get {E} (an energy counter) for each creature you control.
Pay {E}: This creature gets +1/+1 until end of turn.

Bolt Hound

Haste (This creature can attack and {T} as soon as it comes under your control.)
Whenever this creature attacks, other creatures you control get +1/+0 until end of turn.