The term Emperor's Peace is an euphemism for euthanasia in Imperial Low Gothic. It is a bastardisation of the High Gothic term Finis Rerum, that translates to "final thing" or "final service." It refers to the sacred task the Apothecaries of Space Marine Chapters are honor-bound to deliver to a mortally wounded Battle-Brother on the brink of death, namely a swift and merciful ending of his suffering. After the coup de grace has been delivered, the Apothecary removes the Battle-Brother's Progenoid Glands so that he can make his sacred contribution to the continuation of the Chapter. It is from this action that the term Finis Rerum is derived, for the last service a dying Space Marine performs for his Chapter is to ensure its continued future thanks to the precious genetic material he carries within his two Progenoid Glands.
Over time, the term has passed into common Low Gothic usage, where it now refers to any necessary euthanasia of a loyal servant of the Emperor of Mankind for any reason.
The genetically enhanced body of a superhuman Astartes is a marvel of resilience and healing capability, but it has limits, and some wounds are simply too terrible for a Space Marine to survive. When a Space Marine's wounds are beyond the Apothecary's skill to heal, he will speak a few words of comfort to his dying brother before delivering a merciful coup-de-grâce that will end his suffering.
There are multiple ways for the Apothecary to do this; the two most often applyied are either a violent removal of the affected Space Marine's progenoid gland, which destroys both his hearts and lungs in the process; or the use of a euthanasia tool known as a Reductor. This wrist-mounted device that is part of an Apothecary's Narthecium incorporates a powerful spring-loaded piston, which is applied to the wounded Astartes' temple and depressed, caving his head in and causing massive damage to his brain. In both cases, death is almost instantaneous and causes no further suffering to the dying Space Marine.
Apothecaries always administer the Emperor's Peace with a heavy heart, but accept that the harvest of the Space Marine's vital gene-seed will ensure that the dead Marine's legacy lives on through the future of the Chapter.
- Codex: Space Marines (4th Edition)
- Codex: Space Marines (5th Edition)
- The Ultramarines Omnibus (Novel) by Graham McNeill