Partner with Ornsur, Tanarukk Berserker.

Overrun — Whenever a goblin you control attacks, if you attacked with creatures with a total power of 5 or more, amass goblins 1. (Put a +1/+1 counter on an Army you control. It's also a Goblin. If you don't control an Army, create a 0/0 red Goblin Army creature token first.)