Magical Energy is the power source used to actualize the mysteries of Magic.
Magical energy powers almost all types of magic and magi-tech, and it can be comparable to gasoline for magic. The energy in the atmosphere is called Ki, the meaning of which is approximately the same as in Chinese culture. Aether is not a form of magical energy, but instead something else entirely. It cannot exist independently or do anything by itself, so is always bound to some sort of recipient. For that reason, the angels use it mostly by imbedding it into an object or as a catalyst to initiate nature interference spells. The only exceptions to said rule are the Sacred Arms of the Josei and Elves, who recreate miracles by just releasing energy.
Magical Energy is divided into two types, and there is a vast difference between that permeating the natural environment and that generated by an individual.
Ki is the life force of the planet and exists in the atmosphere. It is produced by the world itself. Though Ki is usually found in great quantities, it takes a long time to replenish once it is used up. It is the primary source of energy for Nature Spirits.
If the atmosphere of an area is controlled by something, it is impossible to use large scale spells within the environment because the magical energy cannot be utilized. Only small-scale spells utilizing an individual's internal storage can be utilized.
Mana is the energy found within living organisms such as humans and animals. Once depleted, the Magic Circuits that are stored in the human soul will begin to replenish it. Mana is produced as long as one lives, but the amount a person can store varies from individual to individual.
The difference between Ki and Mana is their abundance. Ki can be found almost anywhere and in great quantities, thus there are many non-Jewels who use Ki techniques in place of magic. As Mana is the energy inside humans and animals, it is much smaller in amount and most Jewels have to go through rigorous training in order to manage it. Strictly speaking, Ki and Mana are energy in its raw state, whereas magical energy is the name given to the energy once it is converted by the Magic Circuits. Ki can be taken in accordingly with the capacities of the Magic Circuits, but the actual conversion process will take time.
Regarding nature interference magic mentioned before, at least for large-scale spells, activation requires the use of Ki regardless of the amount of Mana that the Jewel has. In fact, it is common practice among the Jewels to start up their spells with Mana and then keep them running with Ki. Only small-scale spells that do not interact with the environment directly are performed entirely with Mana, an example of which would be Reinforcement Magic.
Magical energy itself does not have any elemental attribute. However, once imbedded into an object that does have said attribute (such as jewels) or that is under the influence of nature spirits, it will attune itself to the elements in question until the moment that it's released.
The magic energy itself is held only inside the body fundamentally and if released in the world, it will return to life force. This has also been expressed as "evaporation". Magic power is prone to merge with the fluids (such as blood, breasts milk, tears, and semen) of the Jewels, and these fluids are good at holding in magic energy for some time even after leaving the body. Because of this, by drinking a Jewel's breasts milk, one can replenish one's magic power and also increase it exponentially. Jewels with monetary problems have also been said to sell their body fluids, in which magic energy has been merged, to the Foo Fighters.
Effects on the Environment
In nature, the density of mana can be different from place to place. Usually, a location with high mana density would have a penchant for having a distorted environment.