
Goblin Rabblemaster | Creature | Goblin Warrior | Other Goblin creatures you control attack each combat if able.
At the beginning of combat on your turn, create a 1/1 red Goblin creature token with haste.
Whenever Goblin Rabblemaster attacks, it gets +1/+0 until end of turn for each other attacking Goblin. | Svetlin Velinov

Legion Loyalist | Creature | Goblin Soldier | Haste
Battalion — Whenever Legion Loyalist and at least two other creatures attack, creatures you control gain first strike and trample until end of turn and can't be blocked by creature tokens this turn. | Eric Deschamps

Pia and Kiran Nalaar | Legendary Creature | Human Artificer | When Pia and Kiran Nalaar enters, create two 1/1 colorless Thopter artifact creature tokens with flying.
{2}{R}, Sacrifice an artifact: Pia and Kiran Nalaar deals 2 damage to any target. | Eric Deschamps

Scourge of Valkas | Creature | Dragon | Flying
Whenever Scourge of Valkas or another Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn. | Lucas Graciano

Zurgo Bellstriker | Legendary Creature | Orc Warrior | Zurgo Bellstriker can't block creatures with power 2 or greater.
Dash {1}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.) | Jason Rainville

Boros Reckoner | Creature | Minotaur Wizard | Whenever Boros Reckoner is dealt damage, it deals that much damage to any target.
{R/W}: Boros Reckoner gains first strike until end of turn. | Howard Lyon

Sire of Insanity | Creature | Demon | At the beginning of each end step, each player discards their hand. | Joshua Raphael

Ruric Thar, the Unbowed | Legendary Creature | Ogre Warrior | Vigilance, reach
Ruric Thar, the Unbowed attacks each combat if able.
Whenever a player casts a noncreature spell, Ruric Thar deals 6 damage to that player. | Tyler Jacobson

Chromanticore | Enchantment Creature | Manticore | Bestow {2}{W}{U}{B}{R}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying, first strike, vigilance, trample, lifelink
Enchanted creature gets +4/+4 and has flying, first strike, vigilance, trample, and lifelink. | Min Yum