Cecile is the guitar owned and cherised by the King. She is both a fine instrument of music and an impressive tool of destruction. Among the assortment of sounds she can produce is a targeted explosive beam, a glass-shattering pitch, and tones that shake objects out of balance.
It is unknown how Cecile became the musical weapon she is today, but to the King there can be no other. He writes songs that are just as much about her as about himself, pedestalizing her as the one love in his life. Even when he makes his way to the top of the St. Canard criminal milieu over a period of thirty years does he not replace Cecile. Instead, he uses his financial gains to improve her maintenance, going so far as to assign her a lackey to keep her in shape.
Cecile was taken from the King to defeat him. He and his men were sent off to jail, but what happens with Cecile isn't revealed.
The King uses Cecile during a heist on a music store, destroying the safe and surrounding walls with her aid. This act is witnessed by Darkwing Duck and Gosalyn, who've travelled from the future with the time machine. Despite Gosalyn's warning, Darkwing interferes a little, which is enough to upset the course of history so that the King becomes the crimelord of St. Canard. He never parts with Cecile, to which he assigns Drake Mallard as caretaker. One day, he visits the garage owned by J. Gander Hooter and Sara Bellum to demand the taxes for that day. When they refuse to pay, he gets out Cecile and destroys the windows of all cars present. Coincidentally, this moment lines up with the moment from which Darkwing and Gosalyn left on their time journey in the first place and upon returning Darkwing tries to stop the crooks. The King and Cecile make a pile of tires fall atop him, incapacitating him. Realizing they are no match for the King now, Darkwing escapes with Gosalyn back to the past to set things straight. The King's gang escapes him at the music store, but find him spying on them during band practice in their hideout a short while later. Darkwing escapes them, so the gang plans an ambush at Royal Records. Things don't go quite as planned. Darkwing gets his hands on Cecile and defeats the gang with her power.