Bomat Courier

Haste
Whenever Bomat Courier attacks, exile the top card of your library face down. (You can't look at it.)
{R}, Discard your hand, Sacrifice Bomat Courier: Put all cards exiled with Bomat Courier into their owners' hands.

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.

Mountain

Experimental Synthesizer

When Experimental Synthesizer enters or leaves the battlefield, exile the top card of your library. Until end of turn, you may play that card.
{2}{R}, Sacrifice Experimental Synthesizer: Create a 2/2 white Samurai creature token with vigilance. Activate only as a sorcery.

Scalding Tarn

{T}, Pay 1 life, Sacrifice Scalding Tarn: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Kuldotha Rebirth

As an additional cost to cast this spell, sacrifice an artifact.
Create three 1/1 red Goblin creature tokens.

Crack the Earth

Each player sacrifices a permanent of their choice.

Goblin Blast-Runner

Goblin Blast-Runner gets +2/+0 and has menace as long as you sacrificed a permanent this turn.

Gleeful Demolition

Destroy target artifact. If you controlled that artifact, create three 1/1 red Phyrexian Goblin creature tokens.

Arid Mesa

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

Implement of Combustion

{R}, Sacrifice Implement of Combustion: It deals 1 damage to target player or planeswalker.
When Implement of Combustion is put into a graveyard from the battlefield, draw a card.

Goblin Grenade

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

Sokenzan, Crucible of Defiance

{T}: Add {R}.
Channel — {3}{R}, Discard Sokenzan, Crucible of Defiance: Create two 1/1 colorless Spirit creature tokens. They gain haste until end of turn. This ability costs {1} less to activate for each legendary creature you control.

Shrapnel Blast

As an additional cost to cast this spell, sacrifice an artifact.
Shrapnel Blast deals 5 damage to any target.