Play with Fire

Play with Fire deals 2 damage to any target. If a player is dealt damage this way, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Goblin King

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

Aether Vial

At the beginning of your upkeep, you may put a charge counter on Aether Vial.
{T}: You may put a creature card with mana value equal to the number of charge counters on Aether Vial from your hand onto the battlefield.

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.

Krenko, Mob Boss

{T}: Create X 1/1 red Goblin creature tokens, where X is the number of Goblins you control.

Goblin Rabblemaster

Other Goblin creatures you control attack each combat if able.
At the beginning of combat on your turn, create a 1/1 red Goblin creature token with haste.
Whenever Goblin Rabblemaster attacks, it gets +1/+0 until end of turn for each other attacking Goblin.

Foundry Street Denizen

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

Battle Hymn

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.

Legion Loyalist

Haste
Battalion — Whenever Legion Loyalist and at least two other creatures attack, creatures you control gain first strike and trample until end of turn and can't be blocked by creature tokens this turn.

Battle Cry Goblin

{1}{R}: Goblins you control get +1/+0 and gain haste until end of turn.
Whenever Battle Cry Goblin attacks, if you attacked with creatures with total power 6 or greater this combat, create a 1/1 red Goblin creature token that's tapped and attacking.

Goblin Trashmaster

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

Goblin Bushwhacker

Kicker {R} (You may pay an additional {R} as you cast this spell.)
When this creature enters, if it was kicked, creatures you control get +1/+0 and gain haste until end of turn.

Kiki-Jiki, Mirror Breaker

Haste
{T}: Create a token that's a copy of target nonlegendary creature you control, except it has haste. Sacrifice it at the beginning of the next end step.

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.

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Goblin Chainwhirler

First strike
When Goblin Chainwhirler enters, it deals 1 damage to each opponent and each creature and planeswalker they control.

Mogg War Marshal

Echo {1}{R} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Mogg War Marshal enters or dies, create a 1/1 red Goblin creature token.

Shared Animosity

Whenever a creature you control attacks, it gets +1/+0 until end of turn for each other attacking creature that shares a creature type with it.

Goblin Wardriver

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)

Mountain

Smelt

Goblin Piledriver

Protection from blue (This creature can't be blocked, targeted, dealt damage, or enchanted by anything blue.)
Whenever Goblin Piledriver attacks, it gets +2/+0 until end of turn for each other attacking Goblin.

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.

Blood Moon

Goblin Grenade

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

Warren Instigator

Double strike
Whenever Warren Instigator deals damage to an opponent, you may put a Goblin creature card from your hand onto the battlefield.