Spells and Spell NodesEdit
Spells are active exercises of spiritual will, applied through a certain of pattern of thought. Soul Pieces are the the Will and the Power, Spell Nodes are the Pattern and the Knowledge. Without them, casting a spell is impossible.
Spell Variations and SignaturesEdit
Spell Nodes are often difficult to translate from person to person as their logic tends to be based on a person's internal understanding and intuition in relation to the desired effect. Even when magic is taught effectively, the same spell will often have minor differences and affectations based on personal quirks that differ between casters - these are never meaningful as far as the effect of a spell goes, but they are significant in other ways - such as role-playing (a very flashy spell might imply vanity, confidence, or insecurity); sufficient experience with a Caster's style may let someone recognize their spells and link them to certain activities based on the descriptions of those effects, or by examining their results. These "calling cards" become more evident as a caster grows in power - an aggressive mage may have spells that move quickly, leaving little effect before the target, but unleashing immense destruction around and beyond the target, while one uncomfortable with their power might have a furtive, uncertain hallmark to their work. These effects are not so well defined that they count as real evidence in a court of law (though some jurisdictions do allow it to be acknowledged in court, especially if it implies innocence).
Spells and UnderstandingEdit
The other thing to take away from this is that an effect must be understood in a fundamental way - not necessarily in a wholey accurate way, but well enough to convey intent to a well defined reality. The less well understood a concept, the more difficult and draining a spell will be, and it will often come with dangerous or unexpected side-effects. In most cases, if a player can't begin to express what a Spell Node "does," the GM should refuse to let the player have it. Similarly, characters who are uneducated will often have immense difficulties when trying to use less clear-cut and obvious spells; most people "get" fire, and throwing, at least well enough to throw a fireball, but if a character has no idea what atoms are, then attempting to "nuke" anything is pretty bound to fail. This is by far one of the biggest hindrances to using Mind and Quick magics - both are complicated and prone to significant side-effects that are difficult to quantify; becoming even a mediocre practitioner of either is often an exercise in trial and error (which are often lethal in these spell-types), and require great patience and planning (or time). A new practitioner in these spell-types will often aim for simple, not even remotely destructive spells for significant periods of time, testing effects and reactions before moving on to more active and dangerous spells.
The only minor exception to this rule relates to Reapers - as their spells benefit from being destructive, their understandings of a non-combat Spell Node is often more faulty then most - they often have a fairly good general understanding of what they are doing, but rarely learn more. In some cases, this is a personal choice, but often it is the results of a Master intentionally keeping things vague. Some Masters do this as part of their efforts to keep their servants effective but weak, while others, not really understanding the Foci/casting relationship, want every spell to be as destructive as possible to guaranty effectiveness and reliability (this is most often not strictly required - most foci have a broad definition of injury, and any magic that flows from a Reaper's Foci will some how be destructive enough to satisfy the requirements of use, no matter what the Reaper's intent is [assuming the spell works at all; prior testing of a spell is always wise]).
To use a Mind example, a well understood memory erasure spell involves locating the mental framework on which a memory is associated, crossed referenced to the metaphysical or actual location of a specific neuron, and then making careful "cuts" to disassociate the two, probably with a certain amount of re-routing. Reapers will know there's a cell in there for a memory, and that its interrelations are important, and how to approximately find either...and then probably tears them all out magically, resulting in at least some damage to a person's memories and/or associative functionality beyond the desired effect. Since removing a memory is probably destructive enough to satisfy most Foci requirements at this level, this is in no way actually needed. A player/character with only the Reaper's level of knowledge who did not want this to be a damaging/obvious spell would need to do some more research before the GM should let them have it. Most Reapers would be shrug off a spell doing excessive damage (because they;re getting the job done, so why worry?), and most masters would actively discourage learning more to safeguard the abilities of their servants (or may favor that sort of effect for their own reasons).
A Spell Node is a definition of a certain limited family of effects. A Heat Spell Node can light a candle, melt ice, set something on fire, or thaw dinner quickly and evenly. A Water Node allows for the creation, manipulation, and destruction of sufficiently pure water (it also probably can purify a liquid containing water enough to manipulate or destroy the H20 portion of the results). Conversely, they do not give the power to create fire magically (you can heat an area until it bursts into fire, but it doesn't "just happen" (which may give a properly perceptive npc time to evade) and the resulting plasma is mostly uncontrolled), or command mud that is "insufficiently wet" or has another liquid other than water to cause it's current state. While GMs are encouraged to allow a lot of leeway when letting a spellcaster accomplish something magical, these sorts of limitations should be worked out in advance, and held to.
As detailed in Spells, Tiers are a rough estimation of a spells complexity and power. A Heat 1 spell might thaw a pound of meat in 5 minutes, but a tier 3 might do the same for 50 pounds, or it might heat 40 1 pound packets over an area, or 30 1 pound packets, but only on the inside (as a trick for some secret recipe), leaving a quarter inch of frost on the outside of each. As long as the player can articulate an effect, and the GM agrees it's within the bounds of that tier strength, the sky is mostly the limit.
Often a player will name individual spells that they use often - this does not create any additional cost, but is a nice bit of role-playing fluff. For example, the Heat node may have the Spells Thaw, Ignite, Warm (keep an object from becoming colder), and Mirage (causing air distortions through heat, as is common in deserts) under it's umbrella. These are not the only effects that Heat can do, merely the ones that a given player has specifically named and uses regularly. There was no cost for "setting" these spells up, and adding more Spells to the Heat node later may be done freely (though handing a GM a seven page list of Heat spells is probably not useful) - they are mainly a player generated shorthand for commonly used effects. If a player wants to try something new out, it is wise to run it by the GM to make sure it is within the purview of the node, preferably before it's to be used in game.
We're in trouble boss, Do Something!Edit
A GM may choose to allow a spell that isn't within a Spell Node, but is related to one already held, once, especially if the character is under pressure and desperate to make something happen. This is generally accompanied by significant uses of Stamina, well beyond the tier value, possibly followed by fainting and a strict warning to not try that again without the proper node. The idea of someone risking their life to manage crazy things is not to be ignored, especially if the alternative is boring or unamusing (like a total party kill), but player choice, and the consequences of those choices (like not buying a new node and not checking with the GM) are also part of the fun, and adds to the drama of the story. Repeat offenders may be hit with heavier consequences, like physical or psyche damage, an inability to heal, recover stamina, or cast, or even an application of the Death Affliction, entirely at the GM's discretion. Within the story, this is actually an interesting turn of events - how do the other characters respond to the caster slowly falling apart in front of them? Do they think her great, or foolish? Do they want to get stronger, so they can pay back the debt, or do they want to exploit her good will? How does the character feel, having risked death, knowing it is coming closer on each wild gamble? Is it frightening, thrilling, or just another day at the office (fatalism and nihilism are fine characteristics, but do try to help the character sticks with them in a natural way)? Any choice has consequences, after all, and all consequences are interesting, from a certain perspective.