Guilds of Ravnica

Arclight Phoenix | Creature | Phoenix | Flying, haste At the beginning of combat on your turn, if you've cast three or more instant and sorcery spells this turn, return Arclight Phoenix from your graveyard to the battlefield. | Slawomir Maniak

Erratic Cyclops | Creature | Cyclops Shaman | Trample Whenever you cast an instant or sorcery spell, Erratic Cyclops gets +X/+0 until end of turn, where X is that spell's mana value. | Milivoj Ćeran

Rubblebelt Boar | Creature | Boar | When Rubblebelt Boar enters the battlefield, target creature gets +2/+0 until end of turn. | Tomasz Jedruszek

Aurelia, Exemplar of Justice | Legendary Creature | Angel | Flying 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, choose up to one target creature you control. Until end of turn, that creature gets +2/+0, gains trample if it's red, and gains vigilance if it's white. | Chris Rahn

Hammer Dropper | Creature | Giant Soldier | Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) | Lake Hurwitz

Truefire Captain | Creature | Human Knight | Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.) Whenever Truefire Captain is dealt damage, it deals that much damage to target player. | Chris Rallis

Crackling Drake | Creature | Drake | Flying Crackling Drake's power is equal to the total number of instant and sorcery cards you own in exile and in your graveyard. When Crackling Drake enters the battlefield, draw a card. | Victor Adame Minguez