Other players can attack and try to steal resources your resources. Your garrison is automatically populated low level heroes. Supplement it with some high level troops. You can elect to spend 5 silver per troop to assign your best troops to your garrison prior to logging out. You can then reassign them back to your army the next time you play. To disband any of your troops, place them in your Hero's army, then move it to the castle (under the "Available Units" tab in the "Army Recruitment" screen. You will now have the option to sell that troop and get a small amount of silver in return. To improve your troops (by removing negative attribute such as clumsy, lazy, etc.), built the Mercenaries Guild in your castle.