Nightfall Predator

{R}, {T}: Nightfall Predator fights target creature. (Each deals damage equal to its power to the other.)
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Nightfall Predator.

Daybreak Ranger

{T}: Daybreak Ranger deals 2 damage to target creature with flying.
At the beginning of each upkeep, if no spells were cast last turn, transform Daybreak Ranger.

Daybreak Ranger // Nightfall Predator

Savage Packmate

Trample
Other creatures you control get +1/+0.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Child of the Pack

{2}{R}{G}: Create a 2/2 green Wolf creature token.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Child of the Pack // Savage Packmate

Tovolar, the Midnight Scourge

Whenever a Wolf or Werewolf you control deals combat damage to a player, draw a card.
{X}{R}{G}: Target Wolf or Werewolf you control gets +X/+0 and gains trample until end of turn.
Nightbound

Tovolar, Dire Overlord

Whenever a Wolf or Werewolf you control deals combat damage to a player, draw a card.
At the beginning of your upkeep, if you control three or more Wolves and/or Werewolves, it becomes night. Then transform any number of Human Werewolves you control.
Daybound

Tovolar, Dire Overlord // Tovolar, the Midnight Scourge

Dire-Strain Demolisher

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Burly Breaker

Ward {1} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Burly Breaker // Dire-Strain Demolisher

Wing Shredder

Reach
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Bird Admirer

Reach
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Bird Admirer // Wing Shredder

Hollowhenge Huntmaster

Hexproof
Other permanents you control have hexproof.
At the beginning of combat on your turn, put two +1/+1 counters on each creature you control.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Avabruck Caretaker

Hexproof
At the beginning of combat on your turn, put two +1/+1 counters on another target creature you control.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Avabruck Caretaker // Hollowhenge Huntmaster

Ballista Wielder

{2}{R}: Ballista Wielder deals 1 damage to any target. A creature dealt damage this way can't block this turn.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Ballista Watcher

{2}{R}, {T}: Ballista Watcher deals 1 damage to any target.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Ballista Watcher // Ballista Wielder

Werewolf Ransacker

Whenever this creature transforms into Werewolf Ransacker, you may destroy target artifact. If that artifact is put into a graveyard this way, Werewolf Ransacker deals 3 damage to that artifact's controller.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Werewolf Ransacker.

Afflicted Deserter

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

Afflicted Deserter // Werewolf Ransacker

Branded Howler

At the beginning of each upkeep, if a player cast two or more spells last turn, transform Branded Howler.

Convicted Killer

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

Convicted Killer // Branded Howler

Krallenhorde Howler

Creature spells you cast cost {1} less to cast.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Krallenhorde Howler.

Duskwatch Recruiter

{2}{G}: Look at the top three cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order.
At the beginning of each upkeep, if no spells were cast last turn, transform Duskwatch Recruiter.

Duskwatch Recruiter // Krallenhorde Howler

Neck Breaker

Attacking creatures you control get +1/+0 and have trample.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Neck Breaker.

Breakneck Rider

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