In
Shadowrun, a character's
Essence is the
statistic that essentially determines how the integrity of their spirit. As a general rule, it's fairly stable, and most everyday people and animals will have it at a stable 6. As a hard rule, it will never return to its original value once it goes down- even if the conditions that lowered it in the first place are removed.
The most common ways to affect the attribute are through
cybernetic implantations- minor surgery and implantation, such as a
datajack or
cybernetic eyes, is minimal in effect, but more invasive surgery, such as adding
armored plates to your skin, lacing your skeletal system with a
ceramic weave, or installation of an expert system that gives you
inhuman reflexes, will give a significant hit to your
Essence. The spirit can take a good deal of infiltration by the various auras of cybernetics, but push the number to zero or below and
*poof*! it kicks out and you're left with a dead hunk of metal and flesh. Best get out
a new character sheet...
In the case of
mages and
shamans, though,
Essence is a significant number- not only is it directly linked to their capacity to use
magic, it also determines their abilities to stay in the
astral plane. As such, very few
magicians have
cyberware, and even those that do have very minimal implantations.
Paranormal beings sometimes have
Essence, but some don't. Stereotypically "pure" beings like
unicorns have the stat as high as 8, while
harpies often have it at 4. Inhabitants of the
astral plane will have an
Essence stat equal to their
Force, as strong spirits have more presence than their weaker kin.