Granary

Stores crop, and nothing else. A level 20 Granary holds 80,000, and once one reaches level 20 the village may build another - after which each new Granary stands on its own and need not reach 20 before the next.

• Crop arriving above the cap is lost, whether it was grown or carried in by merchants.
• Catapults that take a Granary down take the capacity with it, and any crop above the new ceiling is gone the moment the level drops.
• A second and third Granary are what let a village hold an army rather than merely feed one: a hammer or a well-stocked anvil eats through a single Granary's buffer in hours, and troops starve the moment the balance goes negative and the store empties.
• The buffer is the point. Crop arrives in deliveries and is spent continuously, so the store has to cover the gap between the two - and a village sitting permanently full throws away every delivery that arrives early.
• Enough stored crop also buys time to react: a village with a day of feeding in hand survives a lost oasis, a crop-lock attempt or a few hours offline without losing troops.

Strategy. This is why crop locking works. Destroy the Granaries and a defender cannot hold enough crop to keep an army standing, however much is sent - it arrives and overflows. Attacking the store is often worth more than attacking the troops.

Planning. Size the store against the army, not the village. Work out what the garrison eats in a day and keep at least that much capacity spare before the next reinforcements arrive.

A step pays that much of each of the four resources, plus the hero experience, and the hero's own level adds 2% a level above the first on top of both. A reward can be left unclaimed and taken whenever it suits: claiming it pays no health, but the experience it carries can push the hero up a level, and it is the level-up that restores full health.