"Lay a deadly trap with the Hidden Tesla! Our Wizards have trapped a storm cloud into each of these sneaky towers. When an enemy walks or flies close enough, the tower springs up and fries it using the power of Electrickery!"
The Hidden Tesla is a defensive building with a twist: Similar to a Spring Trap or Bomb, it stays hidden and only appears when a ground or air unit gets close. However, unlike a Trap, it does not have to be rearmed after being deployed.
The Hidden Tesla is unlocked at Town Hall level 7.
Most high level players have them near the Town Hall rather than the storages.
A major source of confusion regarding the Hidden Tesla is that while it has a range of 7, it has a trigger range of 6. The Hidden Tesla will not appear unless the enemy units come within its 6-tile trigger range. The only exception to this rule is that Hidden Teslas will reveal themselves once a base has incurred at least 51% damage, as they must be destroyed (along with all other buildings) in order to achieve 3 stars.
Once the Hidden Tesla is revealed, it will stay visible and attack units out to its maximum range until it is destroyed.
The Tesla does double damage to P.E.K.K.As and prioritizes them over other units.
The Tesla deals the most damage of any defensive building that can target both ground and air units.
The main advantage of the Hidden Tesla is that it is (hopefully) a surprise. Capitalize on that. A well-placed Hidden Tesla can wreak havoc on an attacker's offensive strategy.
Unfortunately many players design their villages such that it has only as many 2x2 open spaces as it has Hidden Teslas available, which makes it obvious where they are located. Instead, try to make sure that there are a few different places where Hidden Teslas could be lurking.
Be cautious when upgrading the Hidden Tesla as this will reveal its location to future attackers. Combat this by relocating it during the upgrade period.
Make sure to place your Hidden Tesla in a space where Troops cannot be placed, as Troops can be placed on a Hidden Tesla.
Before attacking, look for obvious places where a Hidden Tesla might be located and avoid them. Hidden Teslas will only activate when Troops come close to them. If one happens to trigger, keep in mind that it has a low range. If you cannot destroy it easily, avoid deploying more Troops near it if possible, as Hidden Teslas can put out high amounts of damage.
If you see a 2x2 empty square space surrounded by Walls, it is very likely that a Hidden Tesla has been placed there. Be aware that Hidden Teslas are only for Town Hall level 7+.
One Giant and a few Archers can quite easily destroy a Hidden Tesla, as it has relatively low health.
Some people have free places inside Walls, but place a Hidden Tesla to deceive the enemy.
If you have the opportunity to observe a village prior to attacking, such as when planning a revenge, then watch the Villagers. They can reveal the location of Hidden Teslas by walking up to the "empty" spot where the Tesla is hidden and clapping.
Hidden Teslas undergo significant visual changes at levels 4, 7 and 8.
When initially constructed, the Hidden Tesla consists of a tall, slender wooden lattice structure with a wire coiled up one support. The top of the tower has a metal conducting rod protruding from it. On each side of the base of the tower are what appears to be open trapdoors, indicating it buries oneself under the ground until an enemy comes through.
The level 2 and level 3 Tesla gain additional metal conductors hanging down from the top of the tower, and a second wire coiled up the support on the opposite side of the tower.
The level 4 Hidden Tesla acquires its namesake Tesla coil at the top. At level 5, the metal conductor pieces turn golden yellow, and a third coil of wire appears on the front support. At level 6 the Tesla coil itself turns golden as well.
The level 7 Hidden Tesla replaces the Tesla coil with a set of massive horizontal bronze rings. The three smaller wire coils on the tower supports disappear and are replaced with a very thick coil of wire running up the front support. When it fires, the rings glow a steady blue.
The level 8 Hidden Tesla replaces the horizontal bronze rings with a set of lamp-like posts and is black with a yellow glow in the middle. More wires appear wrapped around the building and zaps a few times per minute in your village.
It is not a trap. Some people think it is a trap, but they're permanent structures and you don't need to rearm it even if it is destroyed.
The Hidden Tesla gets its name and appearance from the Tesla Coil, invented by the scientist Nikola Tesla.
A Lightning Spell cannot harm a Hidden Tesla if it has not yet been revealed.
Giants and Balloons will not target a Tesla until it is revealed, even if all other defenses are destroyed.
The Hidden Tesla is the only defense that preferentially targets one unit type (P.E.K.K.A).
The Hidden Tesla can be spawned onto, if it is in a 3x3 square. Placing a troop into the spawn hole will cause the Hidden Tesla to pop up and start attacking.
The Tesla gives off small sparks when it is not attacking and has small electrical wire running up its sides.
The level 7 Tesla has the same top piece as the level 7 Laboratory.
Like the Mortar, the Hidden Tesla can one-shot a similar-level Archer (e.g, a level 4 Hidden Tesla can one-shot a level 4 Archer), with exception of level 5.