Challenger Troll

Each creature you control with power 4 or greater can't be blocked by more than one creature.

Rampaging Growth

Search your library for a basic land card, put it onto the battlefield, then shuffle. Until end of turn, that land becomes a 4/3 Insect creature with reach and haste. It's still a land.

Gaea's Protector

Gaea's Protector must be blocked if able.

Thriving Grove

Thriving Grove enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Rhonas the Indomitable

Deathtouch, indestructible
Rhonas the Indomitable can't attack or block unless you control another creature with power 4 or greater.
{2}{G}: Another target creature gets +2/+0 and gains trample until end of turn.

Drowsing Tyrannodon

Defender (This creature can't attack.)
As long as you control a creature with power 4 or greater, Drowsing Tyrannodon can attack as though it didn't have defender.

Colossal Majesty

At the beginning of your upkeep, if you control a creature with power 4 or greater, draw a card.

Ornery Dilophosaur

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Whenever Ornery Dilophosaur attacks, if you control a creature with power 4 or greater, Ornery Dilophosaur gets +2/+2 until end of turn.

Savage Punch

Target creature you control fights target creature you don't control.
Ferocious — The creature you control gets +2/+2 until end of turn before it fights if you control a creature with power 4 or greater.

Ilysian Caryatid

{T}: Add one mana of any color. If you control a creature with power 4 or greater, add two mana of any one color instead.

Giant Ladybug

Reach
When Giant Ladybug enters, you may search your library for a basic land card, reveal it, then shuffle and put that card on top.

Forest

Roar of Challenge

All creatures able to block target creature this turn do so.
Ferocious — That creature gains indestructible until end of turn if you control a creature with power 4 or greater.