Death's Embrace

When an adventurer is too injured to be operated on normally due to extreme pain or movement a poison called Death's Embrace is used. This thick dark liquid temporarily will kill someone. Allowing them to be operated normally in attempted to cure and heal whatever damage there may have been before giving them the antidote before the damage and effects of Death's Embrace is permanent.
The main reason why this is used is because magic is ineffective against this so it allows the patient to be sedated while any healing magic is channeled into other injuries, poisons, disease, and illnesses. It is not a common answer so it is quite easy to track when made but hard to determine when it is used. Assassins will pay top coin for this medical tool.

Utility

It is used to sedate a patient to a near death state. Since magic is ineffective against it, it will allow the use of healing magic to be more targeted. Assassins try to acquire this poison to either assist in high profile kidnappings or murders as it can fake a death or cause a real one after enough time.

Access & Availability

It is only available to trusted Apothecaries as it hard to produce, administer, and cure. In a given Adventurer's Repose, it is usually the Chapter master and in larger settlements a second member may know the process and procedures.

Complexity

It requires a skilled apothecary to concoct Death's Embrace as well as the antidote. If applied poorly it will result in a permanent death.

Discovery

It's rumored to have been discovered by a Lich during it's pursuit for Lichdom. Deeming it failed experiment left the notes for its creation in a vault which was later discovered by ancient adventurers. After being deemed too dangerous for the public it has been a well kept secret within the medical profession.