At the end of the Second Serpentine War, one Ghost Warrior, Morro, escaped the Cursed Realm and claimed the Allied Armor of Azure, which he used to free several spirits into Ninjago. As Morro fought the Ninja, he was aided by Soul Archer, Bansha and Ghoultar in his quest to claim the Realm Crystal and free the physical manifestation of the Cursed Realm, The Preeminent. Morro would eventually obtain the Realm Crystal, releasing an army of Ghost Warriors into Stiix, which led to a great battle in the city. Soon enough, The Preeminent was released into Ninjago, with Ghost Warriors continuously coming out of it.
The Ghost Warriors constructed a walking mechanism for The Preeminent, allowing her to walk into the Endless Sea with her legion of spirits nearby. When Nya unlocked her True Potential and drowned The Preeminent, the Cursed Realm was destroyed and all those inside it were killed, including the Ghost Warriors who met their true fates in the Departed Realm.
Following the birth of the Cursed Realm, several souls would proceed to arrive at the realm following death, with only the most wicked and vile souls arriving, with the exception of those who were banished using a spell. Being transformed into Ghosts as a result, the Ghost Warriors fell under the command of the Preeminent, the sentient consciousness of the Cursed Realm, and would remain imprisoned for countless years as an atonement for their crimes in life. Later, the Ghost Warriors began preparation for their master's plan to curse the Sixteen Realms, with their Master of Wind and Weapon Masters—Morro, Wrayth, Ghoultar, Soul Archer, and Bansha—being assigned in particular to carry out the Preeminent's plans.
While battling the Ninja over the Scroll of Airjitzu, their commander Morro summoned several of the Ghost Warriors to support him. Initially having the upper hand, the Ghosts were eventually destroyed after Ronin gave the Ninja permission to use his Aeroblades, which, being made of Deepstone, were able to interact with and destroy them, their souls being dragged back into the Cursed Realm.
Summoned by Morro and his Weapon Masters using the Realm Crystal, the Ghost Warriors were tasked with taking over Stiix and defending it from any intruders. Making short work of the citizens by imprisoning, the Ghost Warriors ran rampant, exposing themselves to the luxuries of the living they had missed out on in the Cursed Realm, such as food, music, etc. However, being confronted by the Ninja, the Ghost Warriors fought them, bolstered by the knowledge of their practical immortality, with the Realm Crystal bringing them back to Ninjago every time they died. Though initially unable to stop Lloyd's advance on the Realm Crystal, they nevertheless welcomed the arrival of the Preeminent into Ninjago.
With countless more Ghost Warriors arriving to help in the battle, the spectral entities assisted their master, helping feed her more souls to devour. When the Ninja attempted to drop the Preeminent into the Endless Sea by destroying Stiix's foundations, the Ghost Warriors worked to help their master possess the entire city, allowing her enough immunity from the water to pursue several fleeing citizens out into the ocean, hoping to devour their souls and become even stronger. Attempting to fight off the Ninjas' attempts to thwart their master, the Ghost Warriors failed, with Nya unlocking her True Potential and summoning a massive tidal wave killing the Preeminent and all of them, save thirty survivors, who managed to escape and regroup, plotting revenge.
Seeking vengeance upon Nya for the death of their queen and destruction of their home, the surviving Ghost Warriors attacked Stiix, luring her into their trap as they ambushed her atop a tower. Restricted by the lack of space, enormous height, and lack of allies, Nya began to lose against the Ghost Warriors as they slowly overwhelmed her. However, the Ninja intervened, saving Nya and helping her defeat the Ghost Warriors. Even as they disintegrated, the leader of the surviving group promised to return one day, before being destroyed, leaving all of their souls to rest in the Departed Realm with the rest of the Ghost Warriors.
- The Preeminent (Leader/Queen)
- Morro, Master of Wind (General/Second-In-Command)
- Chain Master Wrayth
- Blade Master Bansha
- Scythe Master Ghoultar
- Bow Master Soul Archer
- Ghost Ninja Attila
- Ghost Ninja Hackler
- Ghost Ninja Ming
- Ghost Ninja Spyder
- Ghost Ninja Howla
- Ghost Ninja Yokai
- Ghost Ninja Wooo
- Ghost Warrior Cowler
- Ghost Warrior Cyrus
- Ghost Warrior Ghurka
- Ghost Warrior Pitch
- Ghost Warrior Pyrrhus
- Ghost Warrior Wail
- Over 500 others and possibly more
Ghost Warriors are constantly intangible, able to pass through solid objects without effort. Because of this, they have to concentrate in order to grasp/move things or people. Ghost Warriors also have the ability to make themselves invisible, however they can still be seen with thermal vision.
Ghost Warriors have the ability to possess objects, mechanisms, materials, and people. This includes the variety of sand, to vehicles, to key holes. Skreemers can possess people by attaching themselves to the head of the person. Likewise, they have the ability to send others to the Cursed Realm if an open gateway is present through physical contact alone.
Most ghosts are able to change between having legs and having a ghost tail. Most ghosts levitate around (with their ghost tails), as opposed to walking with legs. Morro has never been seen using a ghost tail, but has levitated.
Some ghost warriors (notably Morro, Bansha, Ghoultar, Soul Archer, and others) have a variety of weapons that they are able to summon. These are usually melee weapons, with the exception of Soul Archer:
- Serrated Dagger - Bansha, Morro (two)
- Serrated Scythe - Ghoultar
- Double-Blade Serrated Dagger - Bansha
- Bow and Arrow - Soul Archer
- Serrated Flail - Wrayth
- The Ghost Army ties with the Serpentine for the most characters/antagonists released as minifigures. Coincidentally, both factions have a total of seventeen different minifigures, though the Serpentine's are more distinguisable.
- Like the Skreemers, the Ghost Warriors also have a large appetite.
- All of the Ghost Warriors other than Morro and Ghoultar have fangs.
- Morro is the only ghost to never have a ghost tail either due to him being the latest soul banished to the Cursed Realm, or being the Elemental Master of Wind and already having the ability of flight.
- The Ghost Warriors are the second antagonist faction not to eventually become allies with the Ninja, the first being the Anacondrai Cultists.
- Ghosts can actually possess other ghosts.
- Alongside the Serpentine, the Ghost Warriors are arguably one of the few villainous factions to be better off than they were during their initial debut in the series, due to being sent to the Departed Realm following their demise, a far better place than the Cursed Realm.
- In Curseworld, Part II, P.I.X.A.L. calculates there to be at least over 500 Ghost Warriors, and counting. This gives a bare minimum for the number of ghosts at the time.