A Sider is a being that is either Dark, Light, or rarely Twilight.
The origins of a Sider goes back to the time of their original's life and death. When a person is consumed or engulfes themselves in light or darkness, a Sider is then born from that person's very existence. This process is simultaneously fast-paced and efficient, and can birth either a Lightsider or a Darksider.
Biological characteristics of a sider differs between one of light or dark, as one looks evil in dark, or good in light. Their anatomy is virtually the same as their original, with only several differences on what alignment they vary.