"Shields prevent attacks from others. Shields aren't affected by browsing targets in Multiplayer or Revenge, but they will shorten if you start an attack."
2 Hour Guard
1 Day Shield
2 Day Shield
1 Week Shield
What are Shields?
Shields are a temporary period of safety from enemy attacks. While under the protection of the shield, other players will not be able to attack your village. 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:
Automatically after being the victim of a successful Raid (at least 30% damage; see section Automatic Shields below).
Shields prevent attacks against you, but if you start an attack against another player in Multiplayer battles, some shield time will be deducted. 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. The more attacks you conduct under the same shield, the more the shield time will decrease. 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.
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.
Once a Shield expires, you will be automatically given a Village Guard, whose duration depends on your League.
In the Shields section of the Shop, one can find four options:
1 day, 2 day, 7 day Shields;
2 hour Village Guard: The Village Guard functions similarly to the Shields, preventing attacks while it is still active, but there is no penalty to the Village Guard if you do start an attack. However, this is not available if you already have a Shield.
Shields are awarded under two criteria: at least 30% destruction must be done (the destruction of the Town Hall is irrelevant) and at least one-third of a "full army" is deployed. ("Full army" is defined as the max space in camps and heroes (heroes count as 25) of the defender's TH level*). If either one of these criteria is not met, a shield will not be granted.
Depending on the percentage of the village destroyed, the shield time varies.
At 30% destruction, a 12-hour shield is awarded.
At 60% destruction, a 14-hour shield is awarded.
At 90% destruction, a 16-hour shield is awarded.
If the player is in Titan League or higher, the shield time awarded from defenses is reduced.
In Titan III, these shields are 1 hour shorter.
In Titan II, the shields are 2 hours shorter.
In Titan I, the shields are 3 hours shorter.
For players in Legend League that have not signed up, the shields are 4 hours shorter.
You get a free shield courtesy of Supercell, during and after a maintenance break, for a short period of time.
Note that you do not necessarily have to lose a battle to gain a shield; if your opponent destroys between 30% and 49% of your village without destroying your Town Hall, you will gain a shield as well as a defensive victory.
It also doesn't mean that losing a defense gives you shield; if your opponent destroys between 0% and 29% of your village including Town Hall or deploys less than 1/3 of a full army, you lose a defense and you will not gain a shield.
When you start playing the game you get a free 3-day shield, which you should use to get started.
Your 3-day shield is a good time to upgrade your Buildings.
*1/3 full army rule is best described in the From the desk of the devs post on the Supercell forums (Read sections "A Revamped and Improved Shield System" and "Fairer Defenses - Better Raids - More Clash"). As an example, a maxed TH7 can hold 200 troops in army camp + 1 hero (25). A TH7 player will not get a shield unless the attacker deploys at least 75 troops (225 * 1/3), even if the defender doesn't have Barbarian King or 4 L6 army camps. A TH9 can have 2 heroes and 220 housing space, so a defending TH9 needs to be attacked with at least 270 * 1/3 = 90 troops to receive a shield.
If you choose, there is an option to buy shields from the shop for Gems. There are 4 options to choose from. The available options are visually depicted at the top of this page.
Every purchased shield has a cooldown time; the longer the shield lasts, the longer the cooldown period.
Purchased shields have a cooldown period. This was added to keep people from staying shielded indefinitely by continuously buying shields.
The 2-hour Village Guard has a 23-hour cooldown.
The 1-day shield has a 4-day cooldown.
The 2-day shield has a 7-day cooldown.
The 1-week shield has a 35-day cooldown.
If you purchase a shield while you have one currently active, the purchased shield time is added to your current shield time.
If a cooldown is active, you can't purchase another shield or guard.
If you purchase all three shields simultaneously, you will be able to re-purchase additional 1-day and 2-day shields before the end of the initial 10-day shielded period, as the cooldown period on the shorter shields will have expired. This way, the maximum continuously shielded period available via purchase is 18 days ([day 1] 1+2+7 + [day 5] 1 + [day 8] 2 + [day 9] 1 + [day 13] 1 + [day 15] 2 + [day 17] 1). This 18-day shielded period can be purchased every 35 days (the time it takes for the 7-day shield cooldown to reset). Note that if you execute this during a 16-hour shield received from a 90%+ attack or a 12-hour shield received from a 30%+ attack, you can actually increase your total shielded time to a maximum of 18 days, 16 hours, or 18 days, 12 hours, respectively. Also, if you do this during the three-day shield you get when you start the game, you can have a maximum of 21 days on your shield.
Continually buying each shield as soon as its cooldown has expired will result in having 25-26 shielded days every 35-day period, although this will vary from period to period (26 for three periods, 25 the next, then 26 the next three periods, etc.) because the 1-day shield's cooldown will only line up with the other shields' cooldown every four periods. Over a period of 140 days (the minimum time such that all cooldowns line up), one will be shielded for 103 days out of 140 (73.5%).
You cannot buy 1-week shields above 5200 trophies, nor can you buy the Village Guard in the Legend League.
Shields in Legend League
Shields behave differently in Legend League compared to other leagues. There are three fundamental differences:
A player cannot attack under a Shield in Legend League.
Defenses do not give players Shields.
Shields only take effect for whole League Days; this means for each League Day either a player is shielded for the whole of the day or not at all.
This different shield only applies for players that are signed up to Legend League. Players who have not signed up will still have their shields behave in the same way as in lower leagues.