Death's Hourglass is a personal belonging of Death and is said to be an item with equal potency and power to his scythe. Death is known to commonly have an hourglass on him at all times. If multiple people were viewing the glass, it would show different amounts of sand inside, indicating that the individuals who gaze upon it can only see when they themselves will die.
It behaves and resembles an ordinary hourglass, albeit having a Gothic design to it. When viewed by a spirit, they could see the grains being replaced with small bodies of every human, deity, animal, plant, and organism. When these 'grains' drop from above the top of the hourglass, it signifies the birth of this particular being, but when it sinks down to the bottom glass, it rots away and becomes completely lifeless in the process thus showing its death. It also shows the cause of its death, and when it has died as well.
When in the presence of Death, Death can simply see every single species or being in the universe as grains of sand within the hourglass. Death's Hourglass acts like a normal Earthly hourglass, only the difference being is that the grains of sand are in fact the souls of every species or creature that was created or will come into creation. Like an ordinary hourglass, the sand sinks down to the lower bottom of the glass, but to Death this simply shows the time of when the individual will die. When their are multiple grains sinking, it means that thousands if not millions are dying all together or one after the other.
Death's Hourglass is also shown to have absolute control over a person's fate. Meaning that should anyone other than Death wield the glass, they possess dominance over life and death itself over every sentient being in creation down to the microorganisms themselves. Death can manipulate when, how, and where an individual will die via his hourglass, but chooses not to as he knows that doing so will disrupt the Natural Order severely. Usually, those who would be foolish enough to mess with the hourglass, are said to receive a fate "worse than death" according to a Reaper.