Goblin King

Other Goblins get +1/+1 and have mountainwalk.

Quest for the Goblin Lord

Whenever a Goblin you control enters, you may put a quest counter on Quest for the Goblin Lord.
As long as Quest for the Goblin Lord has five or more quest counters on it, creatures you control get +2/+0.

Goblin Traprunner

Whenever Goblin Traprunner attacks, flip three coins. For each flip you win, create a 1/1 red Goblin creature token that's tapped and attacking.

Den of the Bugbear

If you control two or more other lands, Den of the Bugbear enters tapped.
{T}: Add {R}.
{3}{R}: Until end of turn, Den of the Bugbear becomes a 3/2 red Goblin creature with "Whenever this creature attacks, create a 1/1 red Goblin creature token that's tapped and attacking." It's still a land.

Rundvelt Hordemaster

Other Goblins you control get +1/+1.
Whenever Rundvelt Hordemaster or another Goblin you control dies, exile the top card of your library. If it's a Goblin creature card, you may cast that card until the end of your next turn.

Goblin Instigator

When Goblin Instigator enters, create a 1/1 red Goblin creature token.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Mountain

Legion Warboss

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, create a 1/1 red Goblin creature token. That token gains haste until end of turn and attacks this combat if able.

Goblin Matron

When Goblin Matron enters, you may search your library for a Goblin card, reveal that card, put it into your hand, then shuffle.

Goblin Guide

Haste
Whenever Goblin Guide attacks, defending player reveals the top card of their library. If it's a land card, that player puts it into their hand.

Goblin Trashmaster

Other Goblins you control get +1/+1.
Sacrifice a Goblin: Destroy target artifact.

Dogpile

Dogpile deals damage to any target equal to the number of attacking creatures you control.

Goblin Grenade

As an additional cost to cast this spell, sacrifice a Goblin.
Goblin Grenade deals 5 damage to any target.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Goblin Chieftain

Haste (This creature can attack and {T} as soon as it comes under your control.)
Other Goblin creatures you control get +1/+1 and have haste.