
Docent of Perfection | Creature | Insect Horror | Flying
Whenever you cast an instant or sorcery spell, create a 1/1 blue Human Wizard creature token. Then if you control three or more Wizards, transform Docent of Perfection. | Nils Hamm

Identity Thief | Creature | Shapeshifter | Whenever Identity Thief attacks, you may exile another target nontoken creature. If you do, Identity Thief becomes a copy of that creature until end of turn. Return the exiled card to the battlefield under its owner's control at the beginning of the next end step. | Magali Villeneuve

Mausoleum Wanderer | Creature | Spirit | Flying
Whenever another Spirit enters the battlefield under your control, Mausoleum Wanderer gets +1/+1 until end of turn.
Sacrifice Mausoleum Wanderer: Counter target instant or sorcery spell unless its controller pays {X}, where X is Mausoleum Wanderer's power. | Kieran Yanner

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

Wharf Infiltrator | Creature | Human Horror | Skulk (This creature can't be blocked by creatures with greater power.)
Whenever Wharf Infiltrator deals combat damage to a player, you may draw a card. If you do, discard a card.
Whenever you discard a creature card, you may pay {2}. If you do, create a 3/2 colorless Eldrazi Horror creature token. | Daarken

Spell Queller | Creature | Spirit | Flash
Flying
When Spell Queller enters the battlefield, exile target spell with mana value 4 or less.
When Spell Queller leaves the battlefield, the exiled card's owner may cast that card without paying its mana cost. | Adam Paquette

Elder Deep-Fiend | Creature | Eldrazi Octopus | Flash
Emerge {5}{U}{U} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.)
When you cast this spell, tap up to four target permanents. | Jason Felix