The armies fight on their own. Each side has two linked machines in the top frame, and luck decides how they grow.
Fate machine (bottom row): a ball drops every 10 seconds. Split breaks the ball in two for an extra drop and adds a fighter to each wave, Supply speeds up waves, Giant makes fighters bigger.
Weapon fires the ball up into the Armory, which stocks a specific weapon. The more of a weapon you stock, the more often it shows up in your waves.
Champion is locked. Kills earn souls; the number on the lock counts down. Once it opens, a ball landing there summons your champion.
Players can only nudge their team's falling balls. Three nudges, one back every 5 seconds.