It earns on its own, forever. Spend it on soldiers, on walls to ring your base, or on mining upgrades to earn faster.
New soldiers wait safely inside your base. A squad must reach a full 15 before it can move out — the left panel shows READY when it can.
A squad sent to attack cannot be recalled until its target falls. Walls block attackers except where they are broken, so defenders behind a wall have a real edge.
Walled, guarded, and worth +2 gold/sec forever to whoever lands the kill. They never heal or rebuild, so damage sticks — and in team mode you can click an ally's base to donate a soldier.