Rubblehulk

Rubblehulk's power and toughness are each equal to the number of lands you control.
Bloodrush — {1}{R}{G}, Discard Rubblehulk: Target attacking creature gets +X/+X until end of turn, where X is the number of lands you control.

Ripscale Predator

Menace (This creature can't be blocked except by two or more creatures.)

Forest

Alpha Authority

Enchant creature
Enchanted creature has hexproof and can't be blocked by more than one creature.

Slaughterhorn

Bloodrush — {G}, Discard Slaughterhorn: Target attacking creature gets +3/+2 until end of turn.

Skarrg Guildmage

{R}{G}: Creatures you control gain trample until end of turn.
{1}{R}{G}: Target land you control becomes a 4/4 Elemental creature until end of turn. It's still a land.

Scab-Clan Charger

Bloodrush — {1}{G}, Discard Scab-Clan Charger: Target attacking creature gets +2/+4 until end of turn.

Foundry Street Denizen

Whenever another red creature you control enters, Foundry Street Denizen gets +1/+0 until end of turn.

Predator's Rapport

Choose target creature you control. You gain life equal to that creature's power plus its toughness.

Ranger's Path

Search your library for up to two Forest cards, put them onto the battlefield tapped, then shuffle.

Mountain

Pit Fight

Target creature you control fights another target creature. (Each deals damage equal to its power to the other.)

Ground Assault

Ground Assault deals damage to target creature equal to the number of lands you control.

Arbor Elf

Ruination Wurm

Fire Elemental

Zhur-Taa Swine

Bloodrush — {1}{R}{G}, Discard Zhur-Taa Swine: Target attacking creature gets +5/+4 until end of turn.

Dangerous

All creatures able to block target creature this turn do so.
Fuse (You may cast one or both halves of this card from your hand.)

Armed

Target creature gets +1/+1 and gains double strike until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Armed // Dangerous

Gruul Keyrune

{T}: Add {R} or {G}.
{R}{G}: Gruul Keyrune becomes a 3/2 red and green Beast artifact creature with trample until end of turn.

Verdant Haven

Enchant land
When Verdant Haven enters, you gain 2 life.
Whenever enchanted land is tapped for mana, its controller adds an additional one mana of any color.

Skinbrand Goblin

Bloodrush — {R}, Discard Skinbrand Goblin: Target attacking creature gets +2/+1 until end of turn.

Viashino Shanktail

First strike
Bloodrush — {2}{R}, Discard Viashino Shanktail: Target attacking creature gets +3/+1 and gains first strike until end of turn.

Duskdale Wurm

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Centaur Courser

Gruul Ragebeast

Whenever Gruul Ragebeast or another creature you control enters, that creature fights target creature an opponent controls.

Gruul Guildgate

This land enters tapped.
{T}: Add {R} or {G}.

Volcanic Geyser

Volcanic Geyser deals X damage to any target.

Primal Huntbeast

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Ghor-Clan Rampager

Trample
Bloodrush — {R}{G}, Discard Ghor-Clan Rampager: Target attacking creature gets +4/+4 and gains trample until end of turn.