|Weapon of choice||Ghost Katanas|
|First Appearance||Stiix and Stones|
Cowler is a ghost warrior from the Cursed Realm. Like many of the other ghosts, Cowler is just as interested in frightening his foes as he is in defeating them. As the years went on with him imprisoned in the Cursed Realm, Cowler found ways to keep himself occupied.
Perhaps his most notable trick is to imitate the voice of someone's friend to lure them into a trap—something he found humorous while imprisoned but a helpful technique when released from his confinement. Sometimes, he would even imitate Morro's voice to play tricks on the other ghosts. It wasn't until Wrayth had a "long talk" with him that he decided to do otherwise.
Cowler was among the many ghosts released from the Cursed Realm by Morro. He would go on to fight the Ninja and eventually participate in the Battle of Stiix when the Preeminent was freed. Once Nya unlocked her True Potential, she drowned The Preeminent and destroyed the Cursed Realm, along with Cowler.
Note: Due to all ghost warriors being identical in appearance, it is impossible to determine who is who in the television series. As such, any appearances of a ghost warrior will be cataloged here, regardless if they are in fact Cowler.
When Morro used the Realm Crystal to open a portal, Cowler was able to return to Ninjago. He and the other ghosts swarmed the town of Stiix to prepare for the arrival of the Preeminent. He like the other ghosts was incredibly hungry and stole all of the food intended for the imprisoned citizens.
When Wu and Misako arrived in a noodle truck, Cowler and a ghost ninja searched the truck but found it to be empty.
After the Preeminent emerged in Stiix, Cowler and the other ghosts used materials from the town to create a massive mobile suit of armor for their queen that they helped operate to enable her pursuit of the fleeing citizens. However he, his mistress, and the other ghosts were defeated and sent to the Departed Realm by a tidal wave unleashed by Nya.
- Not counting the Ghost generals, Cowler is the only ghost to appear in more than one set.