It is a damage dealing spell that launches a large missile from the King's Tower.
The Rocket is effectively used offensively, to take down Crown Towers with low hitpoints. Therefore, it is a great endgame card, allowing the user to finish off their Crown Tower before the timer runs out.
As a general rule of thumb, if there are or will be units around the Rocket's intended target, aim to hit them all at once. It isn't worth it if the primary target isn't hit, so don't switch targets from the intended one unless a more important target appears.
Because of this, it is not a bad idea to Rocket a deadly troop or supporting units behind a Giant or other tank.
It can take out Elite Barbarians; however, due to their fast move speed making it extremely difficult to aim, this is impractical unless the Elite Barbarians are distracted by another unit.
It is not recommended to use Rocket against swarms of low hitpoint troops. Cheaper alternatives such as Arrows will save on Elixir in that case, as well as have a significantly larger radius. However, Rocket can be used in dire situations to take out a Minion Horde or Skeleton Army.
Use the Rocket to weaken or destroy buildings, such as the Barbarian Hut, to hinder the opponent and also make way for a push. Rocketing the Barbarian Hut also yields an elixir profit.
If not timed properly the Barbarian Hut will still spawn 2 out of 5 waves of Barbarians, but, if timed just right, it will only produce 1 wave of Barbarians. Launch the Rocket when the first Barbarian has traveled 15 tiles. If they plant their hut in the back, launch the Rocket when the first Barbarian crossed the bridge. If it is not placed in the back, keep in mind that the Barbarian Hut takes 14 seconds to spawn. Keep track of the time and send the Rocket after 9 to 11 seconds, depending on where it is placed. Memorizing these timings is important if the player consistently faces spawner decks.
However, the player can aim the Rocket so that it lands on the very edge of the hut, damaging both it and possibly any Barbarians spawned within its radius.
A Rocket can deny up to 8 Elixir from an Elixir Collector up to 2 levels higher than it. Since players usually place their Elixir Collectors in the back, you can destroy the Elixir Collector while also dealing a lot of damage to a Tower.
Rocket is a great counter to X-Bow. It will heavily damage it, if not destroy it by itself, which it will if the Rocket is 4 levels higher.
Even though the Rocket is one of the best ways to destroy buildings, in most cases it is a negative Elixir trade. Therefore, it is important to know when it is a good time to fire a rocket.
The Rocket is difficult to aim and target at moving or flying units, as the spell has a considerable cast time and small damage radius.
Aim the Rocket considerably in front of your target or at the shadow in order to hit it properly.
It is not a wise idea to fire the Rocket at fast troops unless you can aim properly.
Because of this, Rocket pairs very nicely with Tornado. The Tornado will drag most if not all of the desired targets into the Rocket's range. Make sure that the Rocket is launched before the Tornado, and that the Tornado's center overlaps with the Rocket's radius. Remember that certain units resist Tornado more than others, so this tactic may not always work.
The player can also use the Lightning as an alternative, as it has a bigger range and can hit up to 3 targets, along with doing instant damage. The trade off is that Lightning does considerably less damage, and if it is needed to take out a Crown Tower, it will not be as reliable due to it only attacking the three things with the highest health in the area.
If the opponent uses a Rocket, depending on what they hit, it may be a good idea to send an attack down either lane as long as it is not too expensive, due to the fact that they will have to replenish up from four Elixir unless they have Elixir Collectors down.
If your opponent places a Sparky, the Rocket can destroy or cripple it for a neutral Elixir trade.