The Archer Queen is basically a stronger, more powerful version of the Archer. She is automatically summoned once the Archer Queen Altar is constructed. This costs 40,000 Dark Elixir.
The Archer Queen is an immortal unit, so she only has to be summoned once. However, if she is injured or 'falls' in battle, she must regenerate her health by sleeping for a period of time before she can be used again. If you attack a village while its Archer Queen is still regenerating, the Altar will be empty.
The amount of time she sleeps to regenerate is directly proportional to the health she has left at the end of the battle. So if she is not damaged then she is ready to fight immediately; however, if she falls in battle or even gets hit, then she must sleep for some time to regenerate.
The more the Archer Queen is upgraded, the more time it will take to fully regenerate her health.
You can temporarily quadruple the hero's healing rate for 2 hours by spending 10 Gems.
She has better range than an Archer (1.5 tiles more than 3.5 (so 5 tiles)) so a good strategy is to place a group of Giants, P.E.K.K.As or Golems as a meat shield, then a group of Archers and last an Archer Queen. That minimizes the chance of her being defeated or even hit and may allow you to use her many times in a row.
The Archer Queen can be placed next to the Barbarian King to fight together, which will concentrate their power, making them a defensive force to be reckoned with. Alternatively they can also be spaced out to cover a larger range. The appropriate placement depends on what is suitable for your particular village.
The Archer Queen is more suitable for defense, attacks faster and hits harder than the Barbarian King, and does so from a long range (giving her the ability to strike air units), but she has dramatically lower health then the King. Thus, you should place her in such a way that she'll stay behind your walls to harry the attacking troops from a defensive position, as she can't take many hits before going down.
The Archer Queen goes through visual changes at level 10 and 20.
Initially, the Archer Queen is similar to a giant Archer, but with a modified X-Bow, a silver crown, and a green dress.
At level 10, her crown becomes golden.
At level 20, the stock of her modified X-Bow becomes golden as well.
When the Archer Queen is upgrading you can't use her on the battlefield and she can't defend your village.
The Archer Queen shoots 3 rapid arrows per shot (they cannot affect multiple targets, however).
She shoots farther than a normal Archer (5 tiles instead of 3.5).
When she is injured or 'falls' in a battle (attack or defense), a small explosion will occur, she will yell in pain and a red beam will shoot to the sky. After that, she will stand still, having a "dizzy" animation.
The Archer Queen's upgrades up to level 7 cost less than the cost to buy her.
The Archer Queen is basically the counterpart of the Barbarian King, and vice versa. The Barbarian King is the tank specialist, while the Archer Queen is the damage specialist.
As in the January 29th update, the Archer Queen gained a new special ability: Royal Cloak. The Royal Cloak allows her to become "invisible" to enemy defenses for a short period of time, in addition to greatly increasing her damage, restoring some of her health and summoning up to 12 Archers to aid her in battle (although the Archers are summoned by Royal Cloak, they are otherwise unaffected by it unlike the Barbarian King, where barbarians are affected). The Archer Queen gains this ability at Level 5, and it becomes more powerful every five levels she gains.
The Archer Queen's Royal Cloak ability summons Archers of the same level that the player has researched in his or her Laboratory. For instance, if the player has researched level 5 Archers, the Archer Queen will summon level 5 Archers.
If you tap on the Archer Queen she will yell a high pitched battle cry and stand still for a moment, similar to the Barbarian King.
If you put her on sleep mode, when someone is attacking you she won't appear. If you put her on guard mode then she will defend your base while you are being attacked.
While attacking, if your opponent's Archer Queen Altar is empty and the Queen wakes up during your battle, the Altar will sparkle like she is waking but there will be no Archer Queen to defend the base.
If your Archer Queen wakes up while you are in Village Edit Mode, a sparkle will appear wherever the Altar originally was (even if you moved it already).