Royal Ghost

In "Pork-tergeist", being invisible, he creates a cold aura around him that causes a cramp and cold to the people around him, but he can control it.

It is the only troop, without abilities, that can become invisible to others but not to the person it is talking to.

It had an underground arena but it was turned into a themed place where all the other troops could see it (it's like a museum but in IRL), and that displeased the Royal Ghost

Before becoming a ghost, keeping his previous appearance, in his arena he was a somewhat arrogant King who defended himself with his sword, until due to his arrogance and mockery towards the prince of the red team, because he thought he would easily defeat him, he killed him.

The less transparent and less visible it is, the less tangible it is, there is a point where it is half visible but not tangible.

In the 5/11/2018 balance changes reveal video, the text on screen incorrectly states the Royal Ghost's 9% hitpoints decrease as a 6% hitpoints decrease.
The Royal Ghost was originally going to appear in early 2017, with a invisibility mechanic that would dash to the enemy, and reveal himself along with a stun. However, the stun mechanic were dropped, and the dash mechanic lead to the creation of the Bandit. Ultimately, the Royal Ghost was added in one of Clash Royale's updates.

The Royal Ghost is 1 of 14 troops that has been featured with a Rage buff, the others being Electro Spirit, Giant, Zappies, Guards, Giant Skeleton, Goblin Giant, Electro Dragon, Wall Breakers, Electro Giant, Mega Knight, Ram Rider, Electro Wizard, and Sparky.
The Royal Ghost is 1 of 10 troops that has been featured under the Special Delivery ruler ability, the others being Knight, Skeleton Barrel, Mini P.E.K.K.A, Musketeer, Wizard, P.E.K.K.A, Giant Skeleton, Golem, and Sparky.
The Royal Ghost, along with the Minions, Bomber, Skeletons, Skeleton Dragons, Ice Spirit, Mini P.E.K.K.A, Mega Minion, Ice Golem, Dart Goblin, Elixir Golem, Goblin Brawler, Guards, Baby Dragon, P.E.K.K.A, Giant Skeleton, Golem, Wall Breakers, Bowler, Executioner, Mega Knight, Inferno Dragon, and Lava Hound, are featured as a monster in Squad Busters.
He is the 1 of 2 troops that appears in a modifier in Squad Busters, the other being Ice Spirit.
The Royal Ghost is confirmed to be both of the Kings' father. He is also confirmed to be a former King according to the Clash-A-Rama episode "Pork-tergeist".
The Royal Ghost is the subject of certain cosmetics in the game. More specifically:
The Royal Ghost is the subject of 4 Emotes.
In the Trophy Road intro video and the Brief History of Clash Royale video, there was an Emote that showed the Royal Ghost faded into a shadow. This Emote would be obtainable in the Trophy Road instead of the Happy Royal Ghost Emote. However, this Emote never made it to the game.
The Royal Ghost is the subject of a Tower Skin.
A cloned Royal Ghost does not fall from the sky when deployed.
On 27/3/2023, a Trainer was added to the game called Boss Cheddar, and used a Level 18 Royal Ghost in their deck, despite the highest Level being Level 14 at the time. This Trainer was removed on 18/4/2023.

The Royal Ghost may be inspired by the ghost of Hamlet's father from the theatrical play "Hamlet" by William Shakespeare.
The Royal Ghost is 1 of 17 troops that inspired a troop in Clash of Clans, the others being Spear Goblins, Bomber, Bats, Skeleton Barrel, Minion Horde, Firecracker, Battle Ram, Ice Golem, Zappies, Baby Dragon, Giant Skeleton, Ram Rider, Inferno Dragon, Miner, Ice Wizard, and Night Witch.
Unlike his counterpart in Clash of Clans, the Royal Ghost in Clash Royale is always invisible until he breaks stealth and can enter it again after some inactivity, deals medium amounts of area damage with moderate health, but never slows his targets.
The Royal Ghost is one of the first troop cards to receive a card render, alongside the Archers, Knight, Goblins, Bomber, Skeletons, Barbarians, Bats, Royal Recruits, Skeleton Barrel, Rascals, Musketeer, Giant, Valkyrie, Wizard, Flying Machine, Hog Rider, Royal Hogs, Dart Goblin, Zappies, Elixir Golem, Baby Dragon, Skeleton Army, Witch, P.E.K.K.A, Prince, Balloon, Giant Skeleton, Goblin Giant, Hunter, Electro Dragon, Wall Breakers, Bowler, Cannon Cart, Mega Knight, Ram Rider, Miner, Ice Wizard, Magic Archer, Bandit, Lava Hound, Night Witch, and Fisherman.
The Royal Ghost is 1 of 3 troops that can turn invisible and not distract other enemies, the others being Suspicious Bush and the Archer Queen.
The Royal Ghost has been featured in multiple special game modes outside of the card. More specifically:
The Royal Ghost is 1 of 23 troops that has been featured in the Troop Rush game mode, the others being Skeletons, Skeleton Dragons, Fire Spirit, Bats, Elite Barbarians, Firecracker, Rascal Girls, Royal Hogs, Heal Spirit, Elixir Golem, Guards, Prince, Balloon, Golem, Wall Breakers, Ram Rider, Sparky, Phoenix, Bandit, Lumberjack, Santa Hog Rider, and the Monk.