"This colossal menace soaks up huge amounts of damage and bashes anything in his path. He guards his territory fiercely when defending, and can launch into a devastating rage when attacking once his Iron Fist ability is unlocked!"
Levels 1-9
Levels 10-19
Levels 20-40
Levels 41-60
Summary
The Barbarian King is basically a larger, more aggressive, and more powerful Barbarian. He is automatically summoned once the Barbarian King Altar is constructed, which costs 10,000 Dark Elixir.
The Barbarian King is an immortal unit, so he only has to be summoned once. However, if he is injured or falls in battle, he must regenerate his health by sleeping for a period of time before he can be used again. If you attack a village while its Barbarian King is still regenerating, the Altar will be empty.
The amount of time he sleeps to regenerate is directly proportional to the health he has lost by the end of the battle. If he is not damaged (or is fully healed before the battle ends), then he is ready to fight immediately; however, if he falls in battle or is wounded, then he must sleep for some time to regenerate. The more the Barbarian King is upgraded, the more time it will take to fully regenerate his health.
Hero regeneration after a Multiplayer Battle starts as soon as the player starts to search for a Multiplayer opponent. So, if the player spent some time searching for an opponent to attack before completing an attack, part of the regeneration will be completed by the time the player returns to his/her village. However, if the player cancels the attack by pressing "End Battle" before completing an attack, the regeneration will be reset. This effect is more noticeable in the highest leagues where a significant amount of time can be spent searching for such opponents.
The Barbarian King has two modes when defending, "Guard" and "Sleep". In Guard, he will guard the village but will have to regenerate health (sleep) if he takes damage, while in Sleep mode he will not appear to your opponent.
On defense, the Barbarian King only defends his territory around his platform and will retreat if lured too far out.
Starting at level 5, the Barbarian King obtains an ability called Iron Fist which can be used on the battlefield. It partially heals him, summons up to 28 additional Barbarians, and grants the Barbarian King and his summoned Barbarians increased damage and speed. This does not stack with the Rage Spell, and does not affect any other troops, including other Barbarians belonging to the regular army. This ability gets more powerful every fifth level.
If the ability is unlocked, once the Barbarian King is deployed, his icon in the troop deployment window becomes the activation method for Iron Fist. Simply click on his icon again and Iron Fist will be activated.
The Barbarian King summons Barbarians equal to the level of your Barbarians researched in your Laboratory (e.g. if you can train level 5 Barbarians, the Barbarian King will summon Level 5 Barbarians).
Offensive Strategy
The Barbarian King is basically the counterpart of the Archer Queen, and vice versa. The Barbarian King is the tank specialist, while the Archer Queen is the damage specialist, with the Grand Warden as the support specialist.
When attacking, he can be deployed just like any other unit. When he is damaged, he must sleep to recharge before he can be used again. The regeneration time is directly proportional to how much health he must recover. He may be instantly brought up to full health with Gems.
He is best used with support from ranged troops, such as the Archer or Wizard.
He is also good for helping to destroy the remaining buildings of a village after most or all defenses have been destroyed.
The Barbarian King can be easily swarmed by a group of Archers or Barbarians as he only attacks one target at a time and has slow attack speed.
As the Iron Fist ability recovers some health, you should let your Barbarian King take some damage before activating this ability to maximize the recovered health provided by activating the ability.
The Barbarian King can be healed by Healing Spell or a Healer while battling; however, this healing occurs at 55% of the rate of that of normal troops.
Avoid using the ability when the King approaches a Bomb Tower or an area where you suspect a Giant Bomb will be, unless you desperately need to recover health. If you do so, the summoned Barbarians will most likely be wiped out by the resulting explosion.
You can negate the explosion by using the Eternal Tome ability of the Grand Warden, but you may find it more useful to save the ability for tackling a more heavily-defended section of the base.
Defensive Strategy
Set the Barbarian King to "Guard" mode when he is at lower levels as he takes less time to regenerate and will not interfere when you are attacking.
Though he is very strong on offense, he only attacks one target at a time on defense which makes him easy to kill with multiple units, so protect him with splash-damaging defenses.
It is a good idea to place the Altar in the middle of a group of storages or other areas you wish to protect.
Unlike troops in the Clan Castle, the Barbarian King cannot be lured to the edge of the map and then destroyed out of range of the defenses (unless his Altar is near the edge). If his target moves out of his patrol area, he will retreat and engage another enemy inside his patrol area. If no enemies remain in his patrol area, he will resume patrolling.
Although the Barbarian King cannot be lured outside of his patrol range, he will lure attacking troops towards him, sometimes ignoring the structure they were originally targeting. This may be a problem in some cases; if you put the Barbarian King near your Town Hall, the attacking troops can be lured toward the Barbarian King, and consequently get closer to the Town Hall.
Against a Barbarian King
If a defensive King is causing trouble to your troops, use some small troops, such as Barbarians, behind a tanking troop. This will ensure the King is defeated with minimal loss in troops.
If the base has no Archer Queen, or if she is far enough away from the Barbarian King, then attack with air troops, away from buildings that target air troops. You may have to deploy ground troops periodically in order to keep the Barbarian King in an area where your air troops may safely attack the King, so this strategy may not always be effective.
Air attacks such as Balloons and Minions have little to worry from a Barbarian King; he can usually be ignored in such cases. While the Barbarian King cannot retaliate against air troops, he can still distract them away from other valuable targets, such as the Town Hall.
Although swarms of troops are effective against the Barbarian King, the P.E.K.K.A is also effective for taking down low level Barbarian Kings.
You can distract the enemy Barbarian King with troops such as Giants or Golems, and send in high damage troops behind such as Wizards or the Archer Queen. This tactic can defeat the Barbarian King fairly easily.
Upgrade Differences
The Barbarian King goes through significant visual changes at levels 10, 20 and 41.
Initially, the Barbarian King is similar to a giant Barbarian, with a steel crown, steel gauntlet, and steel shoulder guard. He uses a blunt sword with a stone hilt.
At level 10, his gauntlet changes from steel to gold.
At level 20, his shoulder guard's edge turns to gold, and the central spike turns gold as well.
At level 41, his crown also turns gold.
History
He was introduced in the 10/1/13 update, with 30 levels.
The 23/5/13 update added the levels 31-40 for the newly added Town Hall 10, and decreased his upgrade time, regeneration time and upgrade costs on some levels.
The 29/1/14 update added the Iron Fist ability.
The 3/7/14 update reduced the effect of the Rage Spell on the King by 20%, but the Iron Fist ability recovers some health and summons more Barbarians.
The 16/9/14 update has halved the regeneration time relative to before that update (up to level 30).
The 24/5/16 update additionally decreased the regeneration time of all levels relative to before that by a significant amount.
The 19/12/16 update added levels 41-45 for the Barbarian King, and decreased his upgrade costs at levels 31-40.
The 18/12/17 update added levels 46-50 and decreased his upgrade costs at levels 8-45.
The 6/3/18 update changed the mechanics of the Barbarian King's Iron Fist ability; aside from the Barbarian King himself, it now only affects the Barbarians he summons and no longer has any effect on any other Barbarians.
The 11/6/18 update added levels 51-60, and increased the healing effects on the King by 10%.
The 26/6/18 maintenance break reduced the regeneration times across all levels and the upgrade times for levels 39 and below.
Trivia
The Barbarian King only holds his sword in his right hand when he is turned toward to the right sides of the village. When the King turns and faces to the left he is rendered in mirror image, causing his sword and gauntlet/shoulder guard to switch arms. This is done ostensibly to save graphics space.
Every slash he makes on a building or unit creates a mini explosion.
When you tap on him he will yell a low pitched battle cry and stand still for a moment, similar to the Archer Queen and the Grand Warden.
When the Barbarian King is completely healed, a jingle will play, like the Archer Queen and the Grand Warden.
When the Barbarian King 'falls' in battle, an explosion occurs and a bright beam of light is sent up into the sky temporarily. He is then seen standing dazed with stars flying around his head for the remainder of the battle.
Each successive upgrade of the Barbarian King adds approximately 2.5% health and 2% damage, but every five levels also adds a constant three minutes to his total regeneration time. As a consequence, the Barbarian King's regeneration rate changes as he levels up.
Regeneration rate for each level; click to enlarge
The Barbarian King's regeneration rate fluctuates each level, with drops in regeneration rate every fifth level and small increases for every other level. From an initial regeneration rate of 170 HP per minute at level 1, it reaches a maximum of 183 HP per minute at level 4 and shows a downward trend up to level 25, where there is a minimum of 122.96 HP per minute. Beyond level 25, the drops at every fifth level are outweighed by the increases from the other levels, eventually reaching 165.67 HP per minute at level 59 before dropping once more to 158.76 HP per minute at level 60.
The level n Barbarian King's has $ \lfloor120*1.02^{n-1}\rfloor $ DPS for levels 1-40 (however, level 41 and above has a slightly different formula, being $ \lfloor120*1.021^{n-1}\rfloor $ DPS), $ \lfloor1700*1.025^{n-1}\rfloor $ hitpoints.
While attacking, if your opponent's Barbarian King Altar is empty and the King wakes up during your battle, the Altar will sparkle like he is waking but there will be no Barbarian King to defend the base.
The Barbarian King will alternate between hitting the building with the sword and his fist. However, both types of strikes do equal damage.
The Barbarian King was also a part of the Town Hall Level 7 Starter Pack which came with the Barbarian King, a level 3 Hidden Tesla and 1,200 gems which cost $9.99.
