Death Mark
There are forces in the realm of mortals that inspire its name. These effects keep us from living forever, quite actively, in fact. A situation that inflicts lethal trauma upon a creature through physical, magical, or spiritual means could potentially hand them a Death Mark.
When you receive a Death Mark, part of your life ebbs away. A Death Mark first moves you down one stage of the Knockout Track. Second, it occupies that stage; it steals that portion of your energy. Not only do you sustain the −2 penalty to all rolls that a stage of the Knockout Track brings, but you continue to sustain the penalty until the Death Mark is removed.
What that means is that no amount of napping or coffee can unburden a creature of the malaise and fatigue that accompanies a Death Mark. When creatures bear five Death Marks, they gain the unconscious condition. A creature bearing six Death Marks must pay the toll to the ferryman.
Death Marks and The Undead
Normally, only living creatures can hold Death Marks (i.e. creatures of a bestial, humanoid, legendary, or plantlike nature). For undead creatures, Death Marks work in reverse; effects which normally impose Death Marks remove them from undead, and effects which normally remove Death Marks impose them upon undead. An undead creature with five Death Marks gains the immobile condition, a sixth will destroy the creature in dramatic fashion.
Conditional Death Marks
A creature can find itself in circumstances directly harmful to its health that prove fatal if left unchanged. For example: arctic skinny dipping, rooms with no air, or involuntary fasting. Life-threatening circumstances such as these will hand Death Marks to a creature on a recurring interval. Death Marks gathered in this manner are considered fleeting or temporary. If a creature is freed from the harmful conditions (e.g. finding a warm cabin, fresh air, or a hero's feast), the Death Marks and their associated penalties vanish.