Where does "magic" come from?[]
That's simple. It comes from the Root.
Tl;dr
Where is the Root?[]
That's even easier. The Root is located at the core of Mt. Meru, the mountain in the center of the Universe that starts from the Earth and extends beyond the edge of space.
What does the Root do?[]
The Root regulates many functions of the Universe, including the distribution and retrieval of karma, as well as reincarnation.
What is karma?[]
Karma is a particle that collects in the human soul based on their deeds. It comes in two forms- good karma and bad karma.
The Universe was created with equal amounts of good and bad karma particles. The total amount of karma particles in existence is more than the amount of grains of sand it would take to build Mt. Meru.
How do you gain karma?[]
Whenever you do a virtuous or evil deed, the root will distribute karma to you. When you die and are reborn, you retain your past life's karma.
How do you lose karma?[]
Once you die on Earth with enough karma, you will be reborn into a plane of heaven (which totals 26 levels) or the underworld (which totals 4 levels, including 16 sub-layers of hell). Each level is progressively more pleasurable or agonizing than the last.
No mortal can stay in heaven or the underworld forever. You can suffer the worst torture in hell for only a maximum of about 3.5 quintillion years. You can experience pleasure in heaven for even longer than that. But as long as you are not on Earth, the Root will continuously retrieve karma from you. Once you die, your karma is re-evaluated by the Root and you are reincarnated into the appropriate plane. For example, it is possible to die in hell, then reincarnate into a less severe plane of hell.
Trivia: You can only die of old age in hell, and the minimum life span is about 1.5 trillion years.
Hurry up and explain magic?[]
As you have learned, karma is always in flux. Think of karma as the drops of water in a river.
Over the course of human history, we have learned to harness the flow of karma for our own benefit. Think of it as putting a waterwheel in a stream, or a windmill generator in the wind. When we allow karma to flow through our magic circuits, we have access magical energy, or mana.
What is mana used for?[]
Making Mana with Karma
Certain humans can use mana for Magecraft, sometimes called Thaumaturgy, which is the ability to bring about what is possible through science with supernatural means. For example, consider how we understand the phenomenon of fire. As long humanity understands fire, a Magus can use Magecraft to conjure flames from thin air. Though the process is considered a miracle, the end result is not.
Non-humans use mana to fuel their Mysteries, which encompass all supernatural phenomena. This includes everything from flight, to invisibility, to regeneration, to all known feats in legends and myths.