Mob Mentality

Enchant creature
Enchanted creature has trample.
Whenever all non-Wall creatures you control attack, enchanted creature gets +X/+0 until end of turn, where X is the number of attacking creatures.

Kookus

Trample
At the beginning of your upkeep, if you don't control a creature named Keeper of Kookus, Kookus deals 3 damage to you and attacks this turn if able.
{R}: Kookus gets +1/+0 until end of turn.

Keeper of Kookus

{R}: Keeper of Kookus gains protection from red until end of turn.

Suq'Ata Lancer

Haste
Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)

Relentless Assault

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.

Dormant Volcano

Dormant Volcano enters the battlefield tapped.
When Dormant Volcano enters the battlefield, sacrifice it unless you return an untapped Mountain you control to its owner's hand.
{T}: Add {C}{R}.

Song of Blood

Mill four cards. Whenever a creature attacks this turn, it gets +1/+0 until end of turn for each creature card put into your graveyard this way.

Mountain

Goblin Recruiter

When Goblin Recruiter enters the battlefield, search your library for any number of Goblin cards, reveal them, then shuffle and put those cards on top in any order.

Hearth Charm

Choose one —
• Destroy target artifact creature.
• Attacking creatures get +1/+0 until end of turn.
• Target creature with power 2 or less can't be blocked this turn.

Phyrexian Walker

Goblin Swine-Rider

Whenever Goblin Swine-Rider becomes blocked, it deals 2 damage to each attacking creature and each blocking creature.

Fireblast

You may sacrifice two Mountains rather than pay this spell's mana cost.
Fireblast deals 4 damage to any target.