Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Goblin Warchief

Goblin spells you cast cost {1} less to cast.
Goblins you control have haste.

Mountain

Gamble

Search your library for a card, put that card into your hand, discard a card at random, then shuffle.

Gempalm Incinerator

Cycling {1}{R} ({1}{R}, Discard this card: Draw a card.)
When you cycle this card, you may have it deal X damage to target creature, where X is the number of Goblins on the battlefield.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Fire Diamond

This artifact enters tapped.
{T}: Add {R}.

Krenko, Mob Boss

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