“No need to sign for this package! Dropped from the sky, it damages and knocks back enemy Troops before delivering a Royal Recruit. The empty box is also handy for espionage.”
The Royal Delivery card is unlocked from the Spooky Town (Arena 12). It is a defensive Spell played on the player's own side. The Delivery drops from the sky, damaging air units and ground units. Once the delivery has hit the ground, it spawns a single Royal Recruit. A Royal Delivery card costs 3 Elixir to deploy.
The spell has a three second delay after being deployed. Keep this in mind when defending, and time your drop accordingly. This is especially important against the Goblin Barrel. As soon as you see the Barrel coming, place the Delivery right on top of your tower to prevent all damage.
The spell can knock back up to medium sized troops. Hit them with the edge of the spell to maximize the extra distance they have to travel.
Against certain units, like Prince or Sparky, it is effective to place the Delivery right on top of them. The Royal Recruit's shield will protect it from the first blow.
While the spell itself cannot be played past the bridge, it has just enough range to hit a Princess that is standing at the bridge.
The spell is effective at dealing with a Miner swarm combo. Wait for the swarm to get closer to the tower, then drop the Royal Delivery on it. The spawned Recruit will then help deal with the Miner.
Placing it directly on ranged glass cannons such as Musketeers and Wizards right after they cross the bridge will allow the Delivery to counter these troops for a positive Elixir trade. Make sure that the enemy troop stays within range of your Princess Tower.
The spell paired with a building (doesn’t matter if it targets air units) can counter a lone Balloon. Simply pull the Balloon to the middle with the building, and knock it back with the Royal Delivery. This will by enough time for your Princess Tower to finish them off. This still allows death damage, however.
The spell pairs extremely well with Bomb Tower or Goblin Cage on defence. The building will buy time for the Royal Delivery to drop as well as clumping up all the enemy troops, and the knock back as well as the Royal Recruit will distract the remaining enemy units long enough for the Bomb to blow up or the Goblin Brawler to finish them off.