Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.) Haste (This creature can attack and {T} as soon as it comes under your control.) At the beginning of the end step, sacrifice Ball Lightning.

{R}: Goblin Balloon Brigade gains flying until end of turn.

{T}, Sacrifice Goblin Digging Team: Destroy target Wall.

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

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.) When you control a Dwarf, sacrifice Goblins of the Flarg.

Nonbasic lands are Mountains.

Chain Lightning deals 3 damage to any target. Then that player or that permanent's controller may pay {R}{R}. If the player does, they may copy this spell and may choose a new target for that copy.