Departed Realm

The Departed Realm is a realm where beings from the Cursed Realm, Ninjago and the Underworld go after they are destroyed or die.

Day of the Departed
On the Day of the Departed, Cole accidentally used the Yin Blade, which cut a rift in the fabric of reality, allowing departed villains from the Departed Realm, passage into Ninjago, although they could only remain in Ninjago for the duration of the rare Yin-Yang eclipse.

Trivia

 * If ghosts remain in Ninjago for too long without a vessel, they will begin to depart and will then be sent to the Departed Realm.