- Main article: "The Ultimate Enemy"
In the future of "The Ultimate Enemy", Dark Danny develops this power and uses it to bring devastation upon Amity Park. Later, after meeting his dark future self, Danny gains the ability to use the Ghostly Wail himself, and uses his new power to defeat Dan.
The Ghostly Wail is Danny's most powerful technique. With it, Danny can cause massive damage to ghosts and humans alike, and can destroy solid objects or send them flying.
The Wail can completely destroy ghosts that are too weak to withstand it. Dark Danny's ghostly wail was powerful enough to destroy the ghost shield that protected the future Amity Park, which Dan's other powerful attacks could not do.
- When Danny uses this power, it drains his energy extremely quickly. Just one use can leave him with no energy left at all, forcing him to revert to his powerless human form. Inexplicably, he does not suffer this drawback in "Phantom Planet"; it is possible he may have become much stronger and more resilient by this time.
Dark Danny uses this power to destroy Amity Park's ghost shield in "The Ultimate Enemy". When Danny, Sam, and Tucker ended up in Clockwork's lair, he was seen on a screen using it on an army of tanks, blowing them away. He later uses it against Sam and Tucker, but they escaped by using time medallions to return to Clockwork's lair.
In "The Ultimate Enemy", Danny was able to defeat all his old enemies in the Ghost Zone at once with his Ghostly Wail. He later uses it twice in one battle to defeat Dark Danny.
In "Phantom Planet," once Danny regains his powers, he uses his Ghostly Wail to repel all the enemies who were ganging up on him in the Ghost Zone.
It is unknown why he didn't use such a powerful technique against Undergrowth (in "Urban Jungle"), Vortex (in "Torrent of Terror"), or Nocturn (in "Frightmare"). It is possible that he didn't want to risk his attack not having any effect against these extremely resilient ghosts, since he would be rendered defenseless and exhausted if it failed.
- 208. "The Ultimate Enemy"
- 210. "The Fright Before Christmas"
- 215. "King Tuck"
- 217. "Kindred Spirits"