
Master of Waves | Creature | Merfolk Wizard | Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.) | Karl Kopinski

Niblis of Frost | Creature | Spirit | Flying
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast an instant or sorcery spell, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step. | Josu Hernaiz

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

Polukranos, World Eater | Legendary Creature | Hydra | {X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When Polukranos, World Eater becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control. Each of those creatures deals damage equal to its power to Polukranos. | Johann Bodin

Woodland Wanderer | Creature | Elemental | Vigilance, trample
Converge — Woodland Wanderer enters with a +1/+1 counter on it for each color of mana spent to cast it. | Vincent Proce

Notion Thief | Creature | Human Rogue | Flash
If an opponent would draw a card except the first one they draw in each of their draw steps, instead that player skips that draw and you draw a card. | Clint Cearley