Royal Charter
Royal Charter is a synergy upgrade in Loot Grinder, the free medieval idle clicker.
What it does
Every Keep you own boosts your Castle buildings’ output by 0.15%. (Keeps boost Castles by +0.15% per Keep.)
Cost
It costs 15M loot and is a one-time purchase.
Why it’s useful
Synergies scale with how many source buildings you own, so they keep getting more valuable as your kingdom grows.