King Nocturne

The Nocturne was a conceptual being imprisoned inside another universe along with Sutekh and a number of other godlike beings who were a threat to the Doctor's universe. (COMIC: The Jazz Monster)

Biology
The Nocturne was a conceptual being made of living sound. Its true form was that of a monstrous worm-like creature which towered over humans. It had multiple legs, eyes and mandibles and its body was a red colour with a pale outline. (COMIC: The Jazz Monster)

Powers and abilities
The Nocturne, like any conceptual being, was according to the Tenth Doctor, "very versatile". It could manipulate sound for various and creative purposes.

On Wupatki, the Nocturne hid itself as a virus inside songs broadcast from a radio station. The virus could infect the Shan'tee, another race of conceptual beings made of living sound. Once it took over their bodies, it deformed them and they gained a Grim Reaper-like appearance and became mindless killing machines. The virus quickly learned how to infect humans and could even adapt to different counterattacks. (COMIC: The Singer Not the Song)

On Earth, the Nocturne could possess people and link them together to form an incubation field that allowed to fully materialise physically in N-Space. The people it possessed could fire electrical arcs that incinerated the target. It also formed a shield of solid sound around an entire building to prevent anyone from escaping. (COMIC: The Jazz Monster)

Biography
At some point, the Nocturne was trapped, along with many other dangerous entities, in another dimension. These other aliens included Sutehk, an old enemy of the Doctor. Though it tried many times to bargain with the Osiran, Sutehk always refused. The Nocturne thus decided to try to find its own way back into the Doctor's universe. (COMIC: Old Girl)

Its first attempt took place in the far future. It took over a space radio station that broadcast songs across the whole galaxy. The Nocturne hid itself as a virus in songs that were broadcast to the planet Wupatki, a gas giant inhabited by Shan'tee, another race of peaceful conceptual entities whose sound-based physiology made them the ideal hosts. The virus began infecting the Shan'tee and turning them into Nocturne soldiers. The Tenth Doctor, who was visiting Wupatki along with Gabby Gonzalez, discovered the source of the infection and travelled to the station. Before he could find the culprit, the Nocturne deleted itself from the station's database and successfully covered its tracks before fleeing. The Doctor was able to cure the Shan'tee and restore peace to Wupatki. (COMIC: The Singer Not the Song)

The Nocturne's next attempt to enter the universe took place on Earth in the past, in New Orleans, where jazz was just starting to bud. It began possessing people with musical talent such as Paradisa and Roscoe Ramon, with whom Cindy Wu had fallen in love. It then sealed the building off with a force field and linked the people it was possessing together, creating an "incubation field" that would allow it to materialise on Earth. However, the Tenth Doctor and Gabby once again thwarted this attempt but only partially: Paradisa and Roscoe, still possessed, managed to escape and everyone inside the building, except for the Doctor, Gabby and Cindy, had been killed by the Nocturne. It resurfaced two days later in Chicago, where Roscoe was supposed to have a song recorded. The Nocturne planned to plant itself in the song that would then be sold across the world in order to possess more people like it had done on Wupatki. The Doctor and Gabby had managed to travel there the day before using the TARDIS and successfully repelled the Nocturne. This freed Paradisa from its control but it killed Roscoe. (COMIC: The Jazz Monster)

The Nocturne, along with all the other "gods", was released from their prison by Sutehk and converged on the Shining Horizon to kill the Doctor. He managed to contain them inside a suspension field, but the Nocturne broke free and prepared to kill Cindy Wu. Before it could, Sutehk stopped it and disintegrated it, killing the Nocturne. (COMIC: Old Girl)