Ward of Bones

Each opponent who controls more creatures than you can't cast creature spells. The same is true for artifacts and enchantments.
Each opponent who controls more lands than you can't play lands.

Goreclaw, Terror of Qal Sisma

Creature spells you cast with power 4 or greater cost {2} less to cast.
Whenever Goreclaw, Terror of Qal Sisma attacks, each creature you control with power 4 or greater gets +1/+1 and gains trample until end of turn.

Arlinn, the Moon's Fury

Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)
+2: Add {R}{G}.
0: Until end of turn, Arlinn, the Moon's Fury becomes a 5/5 Werewolf creature with trample, indestructible, and haste.

Arlinn, the Pack's Hope

Daybound (If a player casts no spells during their own turn, it becomes night next turn.)
+1: Until your next turn, you may cast creature spells as though they had flash, and each creature you control enters the battlefield with an additional +1/+1 counter on it.
−3: Create two 2/2 green Wolf creature tokens.

Arlinn, the Pack's Hope // Arlinn, the Moon's Fury

Damping Engine

A player who controls more permanents than each other player can't play lands or cast artifact, creature, or enchantment spells. That player may sacrifice a permanent for that player to ignore this effect until end of turn.

Arboria

Creatures can't attack a player unless that player cast a spell or put a nontoken permanent onto the battlefield during their last turn.

Aluren

Any player may cast creature spells with mana value 3 or less without paying their mana costs and as though they had flash.

Vernal Equinox

Any player may cast creature and enchantment spells as though they had flash.

Yeva, Nature's Herald

Flash (You may cast this spell any time you could cast an instant.)
You may cast green creature spells as though they had flash.

Vivien, Champion of the Wilds

You may cast creature spells as though they had flash.
+1: Until your next turn, up to one target creature gains vigilance and reach.
−2: Look at the top three cards of your library. Exile one face down and put the rest on the bottom of your library in any order. For as long as it remains exiled, you may look at that card and you may cast it if it's a creature spell.

Metamorphosis

As an additional cost to cast this spell, sacrifice a creature.
Add X mana of any one color, where X is 1 plus the sacrificed creature's mana value. Spend this mana only to cast creature spells.

Domri, Anarch of Bolas

Creatures you control get +1/+0.
+1: Add {R} or {G}. Creature spells you cast this turn can't be countered.
−2: Target creature you control fights target creature you don't control.