Tesla

“Defensive building. Whenever it's not zapping the enemy, the power of Electrickery is best kept grounded.”

Summary

The Tesla is unlocked in P.E.K.K.A.'s Playhouse (Arena 4).
It is a single-target, medium-ranged defensive building with both moderate hitpoints and damage.
When not attacking, the Tesla will retreat underground, invulnerable to any attacks. However, its lifetime and hitpoints will still decrease.
A Tesla card costs 4 Elixir to deploy.

Strategy

The Tesla is effective against small hordes of troops, such as Skeletons, or slowly zapping away some health from moderate health troops.
The Tesla also deals moderate damage to higher hitpoint troops such as the Baby Dragon. A Tesla can also take out a Lava Hound and its pups without any assistance.
When it retreats underground, the Tesla is unaffected by damage dealing spells, such as the Rocket and Lightning, and cannot be targeted by any troops.
Interestingly, the Tesla can be frozen while underground, so it won't pop up when enemies are in range while the Freeze is active on it. This allows troops to bypass a Tesla and head straight for the Crown Tower, as it can't be targeted while hidden underground.
Tesla is an effective counter to the Royal Giant or Dart Goblin when placed near the river, as they will have to wander into the Tesla's range in order to attack it. So, when using the Royal Giant or Dart Goblin, the player should provoke the Tesla with another troop first to prevent them from wandering into its range and being destroyed.
The Tesla is great at distracting enemy troops that target buildings, such as the Giant and Hog Rider. By placing it in the middle of the player's part of Arena, the troops will target it instead of the Towers if it is not frozen.
The Tesla's re-targeting is rather slow, meaning that the player should send troops in large groups when attacking an enemy's Tesla (like Skeleton Army).
The Tesla can target both air and ground troops and has more health, so it can be interchangeable with the Cannon. It costs 1 more Elixir which is the major downside, however.
It is not wise to attack a Tesla with spells alone, as it will usually retreat before the player can attack it, and even if they do hit it it will result in a negative Elixir trade unless other troops are hit as well. However, freezing a Tesla can help the player hit it with a spell.
Unlike other buildings, the Tesla takes up a 2x2 space as opposed to a 3x3 space. This means that it can fit in the gap between an Arena Tower and the edge of the Arena.
It takes time to get back underground so Spear Goblins can get a hit out of it before they die.
It can support siege towers like X-Bows from your side of the Arena.

History

The Tesla was added with Clash Royale's soft launch on 4/1/16.
On 9/2/16, the Chest Rewards & Card Balance Update increased the Tesla's damage by 7%.
On 29/2/16, the March 2016 Update decreased the Tesla's hitpoints by 5%.
On 23/3/16, a Balance Update decreased the Tesla's hit speed to 0.8 sec (from 0.7 sec) and lifetime to 40 sec (from 60 sec).
On 3/5/16, the May 2016 Update fixed the "range bug" and decreased the Tesla's range to 5.5 (from 6) but its effective range is unchanged.
On 18/5/16, a Balance Update increased the Tesla's hitpoints by 5%.
On 21/6/16, a Balance Update increased the Tesla's hitpoints by 8%.

Trivia

The Tesla's mechanics are similar to its counterpart in Clash of Clans, the level 1 Hidden Tesla which it resembles. However, in Clash of Clans, the Tesla does not retreat underground when it is not actively attacking; it simply remains above ground for the rest of the attack.
The Tesla is the only defense that can be placed symmetrically.
It is named after the Tesla Coil, a device invented by Nikola Tesla which can produce large amounts of AC current in frightening display. However, despite its name the Tesla does not include the namesake device in Clash Royale.
The Tesla is the only building which retreats underground when it finishes attacking.
The word 'electrickery' is a play on words, and a reference to the Tesla's description in Clash of Clans.
Although the Tesla has the same range as the Cannon (5.5 tiles), the Tesla is able to target Musketeers and Princesses due to its ability to become invulnerable when not attacking, forcing them to come into its targeting range before they can target it.
If the Tesla is about to retreat and the Freeze is used on it, the retreating sound effect will loop.
The Tesla is the only Common building so far that can target flying troops.