Walls will halt the spread of grass and delay the progression of all enemies except floaters. They are built to keep the greed at bay while your archers and other defenses kill them off. The higher tier the wall is, the more hits it can take from enemies before it falls. Archers and other units will defend your two outermost walls at night. During the day, damaged walls will automatically be repaired by workers who have no assigned duty.
Tier 0: Dirt Pile
These are naturally generated in random locations on the island, and are the base for where you can build your Walls.
Tier 1: Barricade
Cost: 1 Coin
This wall will barely hold back the Greed before it gets destroyed.
Tier 2: Wood Wall
Cost: 3 Coins
This wall will provide a significant defense against the greed, but will easily be destroyed late-game or during a blood moon. When destroyed, it can be rebuilt for 2 coins.
Tier 3: Stone Wall
Cost: 5 Coins
This wall can provide a great defense against the greed, and will take many hits before falling. When destroyed, it can be rebuilt for 3 coins.
Tier 4: Castle Wall
Cost: 8 Coins
This wall can provide an extremely solid defense against all enemies (except for Floaters), because it takes tons of damage before it falls. When destroyed, it can be rebuilt for 5 coins.
Tier 5: Iron Wall
Cost: 12 Coins
This wall is your best defense against the greed, as it has a ludicrous amount of health. When destroyed, it can be rebuilt for 6 coins.