The High and Low Kingdoms is a term referring to sources or forms of magic and the worlds they are derived from.
In Daventry one of the great principles of magic states As above, so below this is a reference to the High and Low Kingdoms. This is often seen as referring to higher realms (such as the heavens) and lower realms (or underworld) of existence (see dimensions). The physical realm of Daventry itself maybe seen as higher than the underworld, but still lower than the heavens.
This would seem to indicate that it probably has ties to the Left-Hand (black/evil) and Right-Hand (good/white) paths of magic. With one calling upon the divine (gods and angels) for power (however not all 'colors of magic' necessarily originates form the divine) or others calling upon demonic sources or the dead for magic (but likewise not all 'black magic' originates from demonic sources or spirits of the dead necessarily).
The great magician Owen devised a series of magic mirrors in his Floating Castle. The set of three mirrors allows the user to see from one mirror into another, or to even move physically between the mirrors. One was located in the castle's study (in the keep), the second in the great tower (in a small chamber in the first story), and the third was in the quarters of Princess Lydia. To use the mirror one had to touch three symbols surrounding the frame of the mirror in a specific order, and then recite the proper spell phrase; "You are a window through which I can see. You are a door through which I may walk. You are the way between the High and Low Kingdoms. Open, as Owen bade you."
On Earth there are many more definitions as to 'high and low magic' and therefore it is not clear which 'school of thought' is implemented in Daventry in every instance.
Note: There maybe other kingdoms of magic that do not directly fit into this scale, including that of Fairy Kingdom.
Behind the scenes Edit
There are several definitions and uses for the terms 'low magic' and 'high magic' and they do not seem to very consistent and are sometimes arbitrary. Below is a number of these different interpretations;
Perhaps one of the earliest definitions if accurate (seperates High and Low based on essentially 'heaven' or 'hell' from angels or frem demons):
In the Middle Ages of the Near East... part of the Chaldean cosmology involved the existence of an 'upper world' and a 'lower world'. When the Arabs invaded what is now Iraq and enlisted the local to translate both Greek and Nabatean text into Arabic, they became aware of this magical cosmology. They used the word 'ulwee' for higher realm and 'suflee' for lower or underworld. They classified much of the magic that they did as ulwee or suflee. High magic became the magic involving angels and elevated spiritual beings. Low magic became the magic involving demons and evil djinn. It would obviously be hard to use demons for spiritual development, if you belong to JCI persuasion, but you could still use high magic for material gains and benefits. The idea of right-hand path vs left-hand path or white vs black didn't exist in their ancient literature, only high vs low. Many important Arabic texts were translated into English and impacted the development of magic in Europe. Most famous of all is the translation of Emerald Tablet of Hermes that talks about things above being reflections of things below.
See 'what is above
This definition much like the usage in King's Quest novel seem to tie it to both realms (planes of existence/worlds/kingdoms), and possibly morality (light vs dark), left-hand vs. right-hand paths.
However more modern definitions (perhaps influenced by Egyptian, Greek, and Gnostic traditions) tend to shed away the 'morality' from the definitions, and instead apply it to mechanics (or by class rich/expensive ceremonial vs folk remedies). Here are a few modern intereptations;
Ceremonial magic or ritual magic, also referred to as high magic and as learned magic in some cases, is a broad term used in the context of Hermeticism or Western esotericism to encompass a wide variety of long, elaborate, and complex rituals of magic. It is named as such because the works included are characterized by ceremony and a myriad of necessary accessories to aid the practitioner. It can be seen as an extension of ritual magic, and in most cases synonymous with it. Popularized by the Hermetic Order of the Golden Dawn, it draws on such schools of philosophical and occult thought as Hermetic Qabalah, Enochian magic, Thelema, and the magic of various grimoires.
Natural Magic (also referred to as 'low magic') is commonly used by followers of various Pagan paths, ranging from solitaries and Hedge Witches to members of traditional covens. In the past, Paganism was most frequently associated with people of the fields. Since they didn’t have lots of irrigation systems, they needed to be in lower lands where water from rains would accumulate for their crops. As a result, Natural Magic is also known as “Low Magic.” This should not imply that it is in any way lower, of less value, or less spiritual than other forms of magic, only that its European sources were in the fertile lowlands. Natural Magic is the type of magic that uses natural objects from the world around you. This includes such things as herbs, roots, oils, crystals, stones, and various other items. It may include various chants, spells, charms, and incantations and tends to exclude the complexities found in some other forms of magic.
English author and occultist Aleister Crowley often introduced new terminology for spiritual and magical practices and theory. For example, he termed theurgy "high magick" and thaumaturgy "low magick". In The Book of the Law and The Vision and the Voice, the Aramaic magical formula Abracadabra was changed to Abrahadabra, which he called the new formula of the Aeon of Horus. He also famously spelled magic in the archaic manner, as magick, to differentiate "the true science of the Magi from all its counterfeits.
In LaVeyan Satanism, magic collectively known as "Satanic magic" is divided into greater and lesser magic (known also as high and low magic). Greater magic is a form of ritual practice and is meant as psychodramatic catharsis to focus one's emotional energy for a specific purpose. Lesser magic is the practice of manipulation by means of applied psychology and glamour (or "wile and guile") to bend an individual or situation to one's will.
In his 2009 book, Magic and Alchemy, Robert M. Place provides a broad modern definition of both black and white magic, preferring instead to refer to them as "high magic" (white) and "low magic" (black) based primarily on intentions of the practitioner employing them. His modern definition maintains that the purpose of white magic is to "do good" or to "bring the practitioner to a higher spiritual state" of enlightenment or consciousness. He acknowledges, though, that this broader definition (of "high" and "low") suffers from prejudices as good-intentioned folk magic may be considered "low" while ceremonial magic involving expensive or exclusive components may be considered by some as "high magic", regardless of intent.
In some cases people use the terms to refer the way the spells are performed. In this case high magic is magic with much ritual, ceremony and pomp (slow process), while low magic is much more off the cuff, 'natural', emotional, less 'controlled', derived form the natural world ('practical'). But there maybe crossover between both in this definition...