War Machine
War Machine is a synergy upgrade in Loot Grinder, the free medieval idle clicker.
What it does
Every Fortress you own boosts your Citadel buildings’ output by 0.20%. (Fortresses boost Citadels by +0.2% per Fortress.)
Cost
It costs 150M loot and is a one-time purchase.
Why it’s useful
This is a long-game multiplier: its bonus grows automatically every time you buy another source building, with no further spending required.