Sunbane

Sunbane refers to a specific modification to a humanoid's biological make-up that allows the person to absorb and convert ultra-violet light into energy. The leading Ri scientist working on this project envisioned that this would allow for soldiers to survive without food and water, and grant them additional speed, endurance and strength.

However, for various reasons, the project never moved beyond the experimental stage and remained thus fatally flawed - while a subject to which the procedure is applied became able to absorb and store UV light as energy and then expend that energy in various ways, the receptors in the skin that served as conduits for the UV light's energy were simply not able to withstand that the amount of power that came from simple ordinary sunlight. Essentially, they would overload with energy and burst into flames, potentially killing the subject.

As such, subjects would have to avoid sunlight at all costs. However, they could nevertheless increase their power by feeding themselves with small doses of weak UV light.

Over the years, these subjects would give rise to the myth of dark evil creatures that drew their strength from the night and that sunlight - presumably holy - would kill.