Kirian cannot be seen or heard by the average human or monster. He can only be seen or heard by those linked to either death or the Void, those who are close to death, or those who are, extremely perceptive. He can be seen by anyone,when held in a soul container as a soul-shaped cloud but can also take on his normal form. </span>He appears as and has the voice of a child around the age of ten. He appears transparent with very pale skin, curly white hair, and grey eyes. He has no clothing due to the fact that any clothing he finds phases right through him. Fortunately his body lacks any reproductive organs that would require any covering.
Although Kirian looks and sounds like a child, he has the mentality of a well learned adult. This is most likely due to him being around for many many years. Since Kirian is an incomplete human soul, he is unable to emote fully. Any emotions of his own are weak and watered down. The only emotions he can really feel are anger, and fear.
Before disappearing from existence, former Royal Scientist Dr W.D. Gaster designed an experiment to create an artificial human soul in hopes of breaking the barrier (G14 .) At first it appeared to have been a success. While lacking any color, it was clearly human. However, it soon destabilize and remained a cloudy mass inside the soul container. Gaster sighed and left the container on a shelf until he could find a way to make it stable once more. It soon took on the form of a human and watched the scientist in secret, hiding himself whenever someone looked his way for fear of what might happen if he were discovered.
When Gaster was erased from the timeline, Dr Alphys took over as Royal Scientist. Not knowing (or perhaps not remembering) what was in the container, she opened it to investigate. The "soul" escaped and fled the lab. He soon discovered he could sustain himself by absorbing small amounts of energy from sleeping monsters and humans. Over the years he gained a plethora of knowledge and eventually decided to give himself the name Kirian.
- Anyu: Since Anyu is constantly on the brink of death, she has developed a friendship with Kirian. He enjoys her companionship.
- Selenis: The two have actually met but haven't talked much.
- The one who made him.
- Was originally named Jack