Well that depends on the temperature of the area where the body is!
They won't spring up to a sitting position from laying flat, but if they were sitting while rigor mortis was setting, they will be fixed in that position, until mortis relaxes or someone forces them flat.
Metus Mortis was created in 2001.
Hibernus Mortis was created in 1995.
Imago Mortis was created in 2009.
Spiritus Mortis was created in 1987.
Luna Mortis was created in 2001.
Luna Mortis ended in 2010.
Saltatio Mortis was created in 2000.
He who is 'in articulo mortis' is someone on the point of death.
Rigor mortis (literally "stiffness of death") is a natural process within the body after somatic death in which the skeletal muscles become locked in a contracted position. The carcass becomes rigid and unbending. Intoxication with a neurotoxin could affect the development of rigor mortis. For instance, tetanus toxin would cause the animal to be practically in rigor mortis at the time of death because it causes a spastic paralysis where the muscles are contracted during life. In contrast, botulinum toxin might cause the animal to have delayed rigor mortis or even to not develop a full rigor mortis because it blocks the nerves and causes a flaccid paralysis.
"Eater" can be expressed as vorator (genitive voratoris), literally "devourer". "Death" is mors, genitive mortis, so the proper translation is Mortis Vorator or Vorator Mortis. The plural is Voratores Mortis.
The duration of Imago Mortis is 1.88 hours.