Jack-a-Knives

The being known as Jack-a-Knives is a Murder Spirit, the soul of a vicious killer from the ancient world pledged to Hades, Lord of the Underworld. Upon the killer’s death, Hades stripped the spirit of its memories and personality, leaving behind nothing except the desire to kill and the knowledge of how to do it. Some believe Jack is actually an amalgamation or distillation of such dark spirits, gathered over the centuries and fused together in the fires of Tartarus into a single malevolent entity.
For untold millennia, Hades has sent the Murder Spirit to the world of the living to reap souls for the kingdom of the dead. It possesses a living host and becomes a remorseless killing machine, returning to Tartarus when its grisly work is complete, sometimes leaving behind an amnesiac host or hosts, more often leaving just one more body to tie up any loose ends and leave the string of killings unsolved. No one but Hades knows for sure how many infamous killers around the world and throughout history have been hosts to the Murder Spirit, but he’s implied that it has been more than a few. Heroes from the ancient world like Daedalus have encountered the Murder Spirit in many forms and guises.
Jack-a-Knives has been more active in the past century or so as Hades’ vendetta against Daedalus and other mortal heroes has grown. In particular, the Murder Spirit has claimed responsibility for the Ripper murders in 19th Century London as well as an infamous series of killings that took place in Freedom City not long thereafter, which some also attribute to Jack the Ripper. Its more recent killing-sprees include the 1970s and ‘80s, when its host possessed the mutant power to transform into mist, and the combined entity took on the name “Bloody Jack” when it confronted FORCE Ops and other heroes. Later, Jack-AKnives possessed the vigilante known as The Silencer, using his skills and sonic weaponry in a bloody campaign in Freedom City’s South End.
Although heroes have frequently sent Jack-A-Knives back to Tartarus, the Murder Spirit eventually returns to carry out Hades’ schemes, spreading murder and mayhem in the world.

Physical Description

Special abilities

Jack-A-Knives is an incorporeal, shadowy spirit, able to possess a living person, assuming full control over their body and mind. Once the subject’s condition is controlled, they black out entirely, having no memory of the time while Jack is in control of their body. While possessing a host, Jack’s spirit merges with their shadow, disappearing, only visible to those with the mystical or psychic senses to detect it.
The Murder Spirit must take a host while in the physical world; it cannot exist here for long without one. If without a suitable host for a minute, Jack-A-Knives is drawn back down into Tartarus, unable to return to the world for a time (“a turn of season” or about three months). Driving the spirit out of a host and keeping it from taking another is one means of getting rid of it.
While possessing a host, Jack has control over their physical form, able to compel the host to do anything. It is capable of manifesting a knife-like weapon at will with a preternaturally sharp edge, frightfully effective in the hands of a sufficiently strong host, and wielded without mercy.
Attacks upon the host have little effect on the Murder Spirit within: physical damage to the host affects Jack not at all, save that it cannot continue to possess a dead host body, and it will usually abandon a dying or helpless one. Only effects able to target the Will can affect the Murder Spirit within the host body.
There are limits to Jack-a-Knives’ possession: it can only enter the body of an intelligent creature that has killed another intelligent creature or that has come into contact with the “life’s blood” of another intelligent creature. Still, this includes paramedics, trauma doctors, police officers, soldiers, and many others innocents among its potential hosts—including superheroes and villains! It has been known to possess super-powered host bodies on occasion, provided they fit the parameters. The spirit must touch the potential host, either using its current host body or overlapping its incorporeal form with that of the new host.
When the Murder Spirit leaves a host, willingly or not, the host may suffer a heart attack upon Jack’s departure. A host that dies combusts and burns instantly to ash, leaving no trace behind.

Mental characteristics

Intellectual Characteristics

Because the Murder Spirit has no real personality of its own, it relies a great deal on the personality of the host. It exaggerates the host’s own repressed and murderous traits: dislikes become hatred, prejudices become a complete disdain for other life.
The more inclined the host is toward Jack’s murderous work, the easier it is for the spirit to act, so it tends to choose hosts with a suitable temperament, but the Murder Spirit has been known to “hide” in more innocuous hosts for a time, tapping into and exaggerating their own repressed dark impulses. This makes Jack-A-Knives incredibly difficult to find and stop without mystical or psychic aid of some sort.
The Murder Spirit has little regard for its host, and may use it as a hostage against scrupulous heroes; those willing to kill the host in order to get at Jack become potential hosts themselves, opening up whole new options. Jack always knows when someone is a potential host, and tends to go for the strongest host available to it. On at least one occasion, this allowed heroes to trick Jack into possessing the wrong host, thinking it was gaining a more powerful one.
Jack-A-Knives has a sense of haughty artistry about its bloody business, and prefers the opportunity to draw out a kill rather than ending things too quickly. It goes for the kind of elaborate schemes serial killers try to emulate.