A planetary spirit is an administrative entity that oversees a planet's elemental planes.
Planetary spirits are little more than ascended elemental spirits that reside in a planet's core. Each one is chosen either by the previous planetary spirit or the system's solar spirit; the very first spirits were chosen by the Pantheon. Upon selection (or ascension), the spirits are granted permission to execute specific functions required by their position.
The position of planetary spirit was created shortly after the first introduction of elemental planes; it is intended to address the inherent instability of five planes (four elemental, one physical) existing in the same position in space. Without a planetary spirit's administrative functions, the planes will eventually collide, bleed into each other, and then collapse, forming a massive scar that may render an entire solar system uninhabitable. Preventing this kind of catastrophe, as well as other scar-forming events, is one of the Pantheon's primary goals.
Planetary spirits have a number of different responsibilities, all focused on keeping balance among the planes.
Pressure equalization Edit
When raw elemental material is removed from a plane (casting or spirit summoning), or when more than necessary is added back to it (return/rejection of summons or elements), the planar density changes - and with it, the balance between it and the other planes. A planetary spirit may choose to transmute elements into others and distribute them as necessary, or simply vent raw elemental energy into the physical plane. As long as planar density is roughly equal among the four planes, whether higher or lower than the 'nominal' value, the balance can be maintained.
With the exception of the core, where all four elements are present, an elemental plane should only be occupied by a single element. The reason for this is twofold; practicality and culture.
Any caster calling on an elemental plane expects a specific element; allowing the elements to mix too far results in unpredictable results in the physical plane, which is undesirable primarily because it results in a decrease in average magical activity. This decrease weakens the elemental spirits, as well as the planetary spirit, and often leads to unrest and conflict, both intra- and interplanar.
The cultural aspect is a result of the practical; purity is in the long run equivalent to strength, as noted above, so while spirits may planeshift from time to time, they generally clothe themselves in the element of the plane they're on.
Introduction of foreign elements into a plane can be dealt with by the resident elemental spirits up to a certain amount, but beyond that, purification is the planetary spirit's responsibility. In severe cases, a complete rewrite of the planes may be accomplished, which resets the material structure of the planes to a mirror of the current physical plane and forces spirits out of any elemental 'bodies' they currently occupy. This planar reset is meant as a last resort, as it ruins any landscaping or other alterations made up to the point of its execution.
Conflict resolution Edit
Any grievances between spirits, if unable to be satisfactorily settled, are brought to the planetary spirit for arbitration. Due to positional influence, and the recognition of the burden of the planetary spirit's other duties, the judgements made are considered final and unquestionable. In the extremely rare cases where it is deemed necessary, appeals may be directed to the solar spirit.
Planetary spirits rarely manifest in the physical realm, but when one does, it generally appears as a massive pillar of flame or other raw elemental material; flame is the most common, as an imitation of the fiery solar spirits who serve as the planetary spirits' mentors, guides, and supporters.
In its own realm at the core of the planet, the sphere common to all four elemental planes, a planetary spirit often has no physical existence at all since its functions are all accessible through the aether itself, with no physical interaction required. If a physical form is deemed necessary, in the case of visitors for example, it will typically be one constructed of all four elements, constantly shifting in order to keep the necessary balance.