Once a Shield expires, you will be automatically given a Village Guard, whose duration depends on your League.A similar principle will be applied in 'Revenge' attacks after starting the revenge attack by deploying at least one unit, the shield time will be deducted accordingly, regardless of how many troops, spells or heroes were deployed.Conducted attacks will deduct shield time starting from 3 hours then to 4, 5, 6, 8, 10, 12, 16, 20, and then 24 hours, which is the maximum shield time that can be deducted by attacking.

The more attacks you conduct under the same shield, the more the shield time will decrease. If you decide to search for a target to attack but do not actually start an attack (by pressing the 'End Battle' button), the shield duration will remain unchanged. Shields prevent attacks against you, but if you start an attack against another player in Multiplayer battles, some shield time will be deducted.Automatically after being the victim of a successful Raid (at least 30% damage see section Automatic Shields below).At the start of the game, each player begins with a 3-day shield after that shield expires additional shields are gained in one of two ways: While under the protection of the shield, other players will not be able to attack your village. Shields are a temporary period of safety from enemy attacks.Shields aren't affected by browsing targets in Multiplayer or Revenge, but they will shorten if you start an attack.'

Clash of clans clan shield