Flameheart Werewolf

Whenever this creature blocks or becomes blocked by a creature, this creature deals 2 damage to that creature.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature.

Kessig Forgemaster

Whenever this creature blocks or becomes blocked by a creature, this creature deals 1 damage to that creature.
At the beginning of each upkeep, if no spells were cast last turn, transform this creature.

Kessig Forgemaster // Flameheart Werewolf

Ardent Dustspeaker

Whenever this creature attacks, you may put an instant or sorcery card from your graveyard on the bottom of your library. If you do, exile the top two cards of your library. You may play those cards this turn.

Lightning Visionary

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Trailblazing Historian

Haste
{T}: Another target creature gains haste until end of turn.

Null Caller

{3}{B}, Exile a creature card from your graveyard: Create a tapped 2/2 black Zombie creature token.

Ardent Elementalist

When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Tovolar's Magehunter

Whenever an opponent casts a spell, this creature deals 2 damage to that player.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature.

Mondronen Shaman

At the beginning of each upkeep, if no spells were cast last turn, transform this creature.

Mondronen Shaman // Tovolar's Magehunter

Elvish Doomsayer

When this creature dies, each opponent discards a card.

Dragonlord's Servant

Dragon spells you cast cost {1} less to cast.

Dragonmaster Outcast

At the beginning of your upkeep, if you control six or more lands, create a 5/5 red Dragon creature token with flying.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Spellrune Howler

Whenever you cast an instant or sorcery spell, this creature gets +2/+2 until end of turn.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Spellrune Painter

Whenever you cast an instant or sorcery spell, this creature gets +1/+1 until end of turn.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Spellrune Painter // Spellrune Howler

Genasi Enforcers

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
{1}{R}: Creatures you control named Genasi Enforcers get +1/+0 until end of turn.

Dragonspeaker Shaman

Dragon spells you cast cost {2} less to cast.

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Incendiary Oracle

{1}{R}: This creature gets +1/+0 until end of turn.
If a creature dealt damage by this creature this turn would die, exile it instead.

Brallin, Skyshark Rider

Partner with Shabraz, the Skyshark (When this creature enters, target player may put Shabraz into their hand from their library, then shuffle.)
Whenever you discard a card, put a +1/+1 counter on Brallin and it deals 1 damage to each opponent.
{R}: Target Shark gains trample until end of turn.

Arena Trickster

Whenever you cast your first spell during each opponent's turn, put a +1/+1 counter on this creature.