Energy

Energy is a (mostly) form of power that radiates from any being with powers. Found mainly within Great Humans and Demons, it serves as the power source and defining factor on how one's abilities will work in the long run. While it is a constant sort of inner fingerprint for a being, it manifests in three main ways, through Abstract Powers, Demon Powers, and Origin Powers.
Energy is seen as a sort of "soul" for beings. When a being passes away in the Demon Forest, their energy slowly sinks through the ground to its final resting place, a sort of "final death" for the individual. Once the energy reaches the roots of the Demon Forest, it is absorbed into the forest entity and at this point the individual is no longer ever able to be revived again. This can take a few minutes to a half hour, depending on how far down the roots are.
Energy can be sensed by demons and Sensors. Sensors are the only humans capable of even noticing one's Outer color without the abiity to even see it. It is possible to hide one's energy output, but only for a short duration. It is impossible to have powers and not have any noticeable energy output.

Colors of Energy

Every individual with even the tiniest bit of energy within them is born with two energy colors (with one exception). These are known as Inner and Outer energy colors. The combination of these two colors within an individual can be used as a sort of identification, in this world where transforming into other beings can be quite natural.

Outer Energy Color

Unseen to the naked human eye, this is a constant radiating color that appears as a sort of fingerprint for individuals. Demons can see these colors clearly with their vision, but there are very few cases of humans ever being able to see these. This is the color that is believed to be the soul of an individual. It has been described to have an almost "fluffy" or "fuzzy" appearance, almost like seeing static in the place of someone. This can be thought of as a sort of unseen mirror image of the individual, mimicking their current state. If the individual loses an arm, their fuzzy Outer color will appear to have lost that arm as well.

Inner Energy Color

Inner energy colors start appearing whenever an individual is using any sort of power. This is believed to be the main energy from which all powers originate. The stronger the power, the brighter their Inner energy will glow, up to the point of sometimes becoming visible. This energy, when used, has been documented to radiate from within in the form of veins spreading throughout the user's entire body, almost as though it had its own veins to follow through the human body. From intense studying, these have been found to coil around the body's veins when in use. If a limb is lost, the individual loses the ability to use their powers with any prosthetic in place of the original limb.
Synthetic energy conduits have been in the works for many years now and with the right amount of money, it is possible to get a prosthetic capable of functioning exactly like the original appendage, including the use of powers.

Special Energy Colors

• White Energy Color: An unnaturally occurring color that is actually a gift given to those The Lake Spirit finds worthy. It is her signature energy color and the only one she has. In humans this appears as a lighter tone in their usual energy colors, mainly a white border around their being. In demons, it is nearly unnoticeable unless confirmed by The Lake Spirit.
• Black Energy Color: A sign of Corruption in humans, but a naturally occurring absence of color in demons. It is known to exist due to it being confirmed by demons and being the only energy color that makes itself visible every time powers are used, mainly having an appearance of deformed hand prints or long arms.

Energy Within Humans

Energy is only found within a select few of the human population, mainly within Great Humans. While it is possible for an Ishallan to develop powers through prolonged contact with humans, it mostly results in the individual passing away after a short period of time, for they cannot handle maintaining energy inside themselves for any safe period of time. Corruption does lead to the development of new powers within humans, however it is extremely rare and stories of survival are even rarer.
For those who are lucky enough to be born with energy, there are two determining factors on just how successful the individual will be in their future in regards to their abilities. Those two determining factors are their Capacity and Regeneration.

Capacity

This refers to just how much energy can be safely stored in an individual's body before it has a possibility to become harmful or toxic to others from lack of use or improper control. It is like comparing a cup of water to a bathtub, some containers simply hold more water than others. This cannot be changed throughout one's life, but it can be worked around through training with one's abilities. Put simply, Capacity determines the maximum achieved strength possible.

Regeneration

This refers to how quickly an individual can refill their energy after using their powers. A cup and bathtub can be filled at the same speed so they fill at the same time, or the cup can be filled quicker than the bathtub. It's all up to chance and proper care. Unlike Capacity, Regeneration can change due to prolonged power usage as well as certain Abstract Powers. To put it simply, Regeneration can determine the duration of powers being used.

So what does that all mean?

↓ Capacity ↓ Regeneration
The individual might not even be aware of the powers they cannot use, due to an abysmally low amount of energy within them, leaving them completely drained before bringing out any amount of energy within them. Demon Powers are most likely impossible to use in this situation, and even if they are able to use their powers, they cannot compete with an individual with the same potential with higher Capacity and Regeneration. These users are not fit to be anywhere above C rank unless they have any sort of Abstract Power that makes up for their abysmal energy Cap and Regen. Origin Powers are also most likely out of the mix, as they deal with energy in a very similar way compared to Demon Powers. Unsuited for high energy costs and maintained powers.
↑ Capacity ↓ Regeneration
The individual might have some luck in improving with their powers. With a high capacity, one can use a multitude of powers before tiring out, however with lowered Regeneration they will need more rest than someone with increased Regeneration. Depending on the amount of energy stored within them, they can outlast even hardy foes, but in the end they will more than likely grow tired much quicker regardless. For some, if the Capacity is enormous, they might never notice how they start running out of energy, if they ever do reach that point. With a large Capacity, even very slow Regeneration can still prove to be quite helpful. These individuals will most likely be able to use most Demon Powers, Origin Powers, and Abstract Powers. Unfortunately, people in this situation would most likely have great difficulty becoming Healers.
↓ Capacity ↑ Regeneration
These individuals face the opposite sort of issues compared to the previously mentioned ones. With lowered Capacity and heightened Regeneration, these users will be able to outlast many, if not most foes they come across. The downside to this being is that they will forever be limited to low-energy powers. Most Demon Powers would be accessible to them, including Healing, however they would be more successful at maintaining a constant Healing aura rather than any surgical procedures, let alone revival. Origin Powers would most likely be out of the mix, for many of those require high energy users. Abstract Powers are always on the table for these individuals.
↑ Capacity ↑ Regeneration
The cream of the crop, the best possible combination one could have. High Capacity and high Regeneration means that all powers across all three categories are on the table, and the rest depends on the individual alone to learn. They can outperform nearly anyone with a possible negative to either Capacity or Regeneration. These users make the best Healers and the best fighters. They also make up some of the most destructive Origin and Abstract users.

Energy Within Demons

Demons, as beings created entirely out of energy, all have high Capacity and quick Regeneration. Some are noticeably more powerful than their brethren. Weak demons are not uncommon however, as smaller demons have a tendency to be weaker than larger demons. Their Inner and Outer energy colors change periodically and change depending on mood (mainly excitement), and possibly for attracting partners. Demons still maintain a specific two colors per individual, similar to how humans do as well, and generally these come out during periods of relaxation and using their powers.