Bonetorn

"So tell me, Lady 'Roya', what are you here to waste my time for?" The man gniffled, an attitude not fitting with his large muscles and vicious looks. His henchmen spread around the club did the same, a sound barely audible over the humming of the fog machine and background music.
In return, Roya just gave him a faint smile. "I just came to have a final word with you, Mad Dog Tassell, since you insist on getting in my way."
"Ah, so that's why you decided to poison my drink? What, did you think I would not hear about you purchasing a large quantity of Bonetorn? I'm a frequent buyer myself, of course I'd be informed." He grinned maliciously at her, like a toxic beast grinning at his defenseless prey.
Roya shook her head in response, never letting that faint smile leave her face. "I'm afraid you're wrong there. I would never be foolish enough to try to poison your drink." She took a moment to take both drinks on the table, then slammed them back one after the other. "Besides, I'm immune to Bonetorn."
"Bullsh-" he said as he slammed the table, then his voice turned into a painful scream that kept going in a mad panic. She still smiled at him, while his henchmen were too shocked to act. When the screaming continued, some finally found the mental wherewithal to rush forward. As their first rushed steps landed on the floor, they crumbled into a screaming mess themselves. This in turn led to a panic escape attempt by others, all immediately meeting the same fate.
Surrounded by screams, with just a few of the dozens of men still standing, Roya rose to her feet. She walked over to the stage and grabbed a microphone, cranking up the volume so that everyone could hear her over the screams that were slowly turning into whimpers. "I put it in the fog machine. Sure, it meant a lot of collateral damage, but it's not as if your goons didn't deserve it. Remember this as you suffer and die, Tassell. When you choose your weapon, you choose your own death."
The last men standing were frozen in fear, realising the horrible fate that awaited them, having witnessed it plenty of times before. They did not even dare to turn as Roya walked past them, softly whistling as she left the club, its screaming, and all its living dead behind. If they were lucky they'd die fast, their sharded bones cutting arteries and causing them to bleed out.
She hoped luck would not be on their side.

— Tales of the Ruthless

Boneshard originally was a natural pathogen discovered on Ophiuchus 58. It would infect large herbivores, slowly feeding on their bones and softening them. Eventually the creatures' bones would fail and break into thousands of small shards. Death was slow and painful, unless the shards got into places of the body that quickly killed.
After the death, as none would approach as a creature died screaming, scavengers would consume the corpse. Many would die in turn, but some were immune and would spread the pathogen through their feces.
The pathogen was discovered by local scientists, who studied it carefully in hopes to find a cure. Then, one of them decided to weaponize it instead. The final result, thousands of deaths later, was brought to market as Bonetorn. After a few terrorists used it in mass murders, the entire planet and almost everyone involved in its production were turned to ash. However, some escaped and carefully kept selling lower quantities.

Names

Bonetorn, originally Boneshard

Cause

Biogenetically enhanced bacteria

Vectors

Inhalation, Ingestion

Lethality

100% unless immune

Treatment

Unknown

Legality Of Use

Death Penalty in all jurisdictions

Sold Bonetorn was engineered to be incapable of reproducing on its own, making sure none could cut out the sellers. It struck far faster than its original version, making bones brittle enough to shatter within half an hour. Victims would break bones at the slightest bump, being in incredible pain as the shards dug through them. A painful reaction could cause a chain reaction. With its vectors being both inhalation and ingestion, there were plenty of ways one could be exposed to it.

Bonetorn was used in assassinations with spiked drinks, though many of the rich and famous would use detectors just in case. The space pirate Mad Dog Tassell was known to use it on anyone he extorted that did not give up their money fast enough. He died after a run-in with Roya, CEO of Cetus Corp, when she supposedly turned his own weapon against him. Given how there have been no known Bonetorn exposures in the four years since, it is suspected that she then had the entire supply chain destroyed.