Take 2.
Spellcasting
Spellcasting is a collection of techniques, knowledge, and grimoires passed down over the years and continually improved upon, until at last it settled into its current form, divided between those who wield arcane magic, those who receive gifts from the gods, those who worship nature, and the lucky few who just have a little bit of a knack for it.
Unlike in other settings, Arhosan spellcasters use a more fluid form of magic. Rather than learning and using premade packages of magical energy, Arhosan spellcasters learn to manipulate the fundamental building blocks of magic, combining them together dynamically. Each spell seed represents one aspect of magical energy that a spellcaster can make use of. When a spellcaster casts a spell, she employs the seeds she knows, combining them as best fits the situation and her needs. A single spell may be made from a single seed, or may contain the effects of multiple seeds together, their powers mixed for greater synergy.
Arhosan Magic and Traditional Magic
Arhosan spells generally follow the same rules as traditional magic spells. They provoke attacks of opportunity to cast, require a Concentration check if disrupted, can be dispelled and counterspelled, and so forth.
Spell Points
Arhosan spellcasters manipulate raw magical energy. The amount of energy a spellcaster has at her disposal is measured in discrete quantities called spell points (or SP), similar to, although distinct from, a psionic manifester's power points. More powerful spells cost more spell points.
A spellcaster can only spend up to her caster level in spell points to cast a spell. She cannot cast spells that cost more spell points than that, even if the cost she must pay to cast them is reduced.
Each spellcaster has a pool of spell points. She spends these spell points to cast spells. A spellcaster can generally refill her pool and recover lost or expended spell points once per day, although the exact nature of this process varies from spellcaster to spellcaster. A spell point pool may never have more spell points in it than its size. If it does, any excess spell points are immediately and irrevocably lost. Changes to the size of a spellcaster's spell point pool may thus reduce the number of spell points she has remaining, but never increase it. The size of a spell point pool may never be less than 0, however, regardless of what modifiers are applied to it.
Bonus Spell Points
A spellcaster can gain bonus spell points for having high ability scores. She increases the size of her spell point pool by her caster level x her relevant ability bonus (if any) x 1/2 (rounded down).
Spell Seeds
An Arhosan spellcaster knows one or more spell seeds. Each seed has one or more effects, each of which has a value in spell points. Most spell seeds can be enhanced by pouring more raw magical energy (spell points) into them. A spell seed also indicates how it is used. Some seeds can only affect individual creatures, others can fill entire areas, and many can be manipulated to do either. Some seeds produce effects that flare up and finish in an instant, others produce lasting magical effects. Generally, only spell seeds that act in generally the same manner (in an area, producing an emanation, affecting individual targets, etc.) can be combined together into a single spell, although many common techniques have been developed to combine different types of seeds together, albeit in somewhat limited ways.
Seed Type
Each seed has one or more overt magic types through which it can operate. A spell can only contain seeds of a single type. Most seeds can operate as multiple types, although a given spellcaster generally learns only to use a single general sort. The seed type used determines the type of magic the spell produces: arcane (arcane, skill), divine (divine, nature), or neither (artifice, pact, etc.). Arcane spells are subject to arcane spell failure, as normal, although skill-casters usually learn techniques to mitigate this, at least in lighter armor.
School
A seed indicates its school of magic. A spell is of the school and subschool of its seeds. If it has multiple seeds from multiple schools, it is a multi-school spell (PHB2) from each of them.
A seed that does not indicate its school does not alter a spell's school of magic (leaving it as a universal spell if no schools are applied by any of its seeds).
Descriptor
A seed may have one or more descriptors. A spell has all of the descriptors of all the spell seeds it uses.
A seed that does not indicate its descriptors does not have any.
Range
Not all seeds are compatible with all ranges. This entry indicates which ranges a spell containing the seed can use.
A seed that does not indicate its range is compatible with all ranges except for unlimited range.
Targeting
Different seeds can be applied in different ways. Some target individual creatures or objects, others affect entire areas. This entry indicates which category of targeting types a spell containing the seed can use. Some seeds further restrict targeting to a specific type within a category. Some types of targeting allow for multiple seeds of differing targeting types to be combined into a single spell.
Duration
Some seeds produce effects that are instantaneous. Others produce ongoing or continuous effects. This entry indicates which is which. Some seeds are further restricted to spells of certain durations.
A seed that does not indicate its duration is compatible with all non-instantaneous durations.
Saving Throw
The seed's saving throw. This indicates what type of save is allowed (if any) against the seed's effects. The effects of the saving throw only apply to the seed's effects, not to the spell as a whole nor to the effects of any other seeds the spell may use, even with abilities such as Evasion and Mettle.
Creating a Spell
A spell is created first by selecting the overall power level of the spell (how many spell points it costs), then defining the spell's characteristics (type, casting time, range, targeting, and duration), and finally choosing one or more known spell seeds.
The total value of the spell's characteristics may not exceed the spell's cost. Likewise, the total value of all spell seeds used cannot exceed the spell's cost. The values of each group (characteristics and seeds), however, are independent.
A spell must always use at least one spell seed, and must always have a cost of at least 1.
A spellcaster cannot create a spell that she cannot cast.
School of Magic
Most Arhosan spell seeds impose a school of magic on the spells they produce. While they usually manipulate magical energy in a less codified manner than normal spells, they usually follow earlier principles of later magical development, and thus produce spells that are functionally of one school or another.
A spell using only seeds that are not from any schools of magic is a universal spell.
Descriptors
A spell has all of the descriptors of the spell seeds it uses.
Spell Level
A spell's level is equal to 1/2 the spell's spell point cost (rounded up), to a maximum of 9th-level for a spell that costs 17 or more spell points. Thus, a spell with a cost of 1 or 2 points is 1st-level spell, one that costs 3 or 4 points is 2nd-level, and so on.
Components
A spell has both verbal and somatic components. Some spell seeds may add additional components.
Casting Time
A spell's casting time can be as little as 1 immediate action to as long as several hours.
Range
A spell's range must be compatible with each of its spell seeds.
Aiming a Spell
A spell's targeting must be compatible with each of its spell seeds.
Some special targeting options combine seeds of multiple targeting categories. Even if a spell seed can be used with more than one of these categories, it only counts for one of them. A spell can make use of the same seed multiple times (each instance of the seed counting against the maximum value of spell seeds, and potentially having a different spell point value assigned to it), each applying with a different targeting type.
Duration
A spell's duration must be compatible with each of its spell seeds.
Some targeting options produce a secondary effect with its own independent duration, separate from the spell's main duration. If the secondary effect directly carries the effects of any spell seeds, it must be compatible with those seeds. Otherwise, it can have any duration.
Saving Throws
A spell's save DC is equal to 10 + its level + its caster's relevant ability modifier (or Charisma if unspecified and for spell-like abilities).
Spell Resistance
A spell is normally affected by spell resistance.
Some seed effects ignore spell resistance. A spell containing only seeds that ignore spell resistance is not subject to spell resistance.
A spell containing a mixture of seeds that are subject to spell resistance and that ignore spell resistance still checks against spell resistance. Only the seed effects that are subject to spell resistance are negated by it. Those that ignore spell resistance still apply, even if the spell failed to bypass the subject's spell resistance.
Spells with Multiple Seeds
A single spell can make use of multiple seeds (although always at least one). Each seed produces its effects as part of the spell. If order is important, the spellcaster can determine the order when creating the spell.
A single spell can even have the same seed applied multiple times for different effects. Each instance of the seed counting against the maximum value of spell seeds, and potentially having a different spell point value assigned to it. The effects of the same seed applied multiple times to the same spell never stack. If the same effect if applied at different strengths, only the strongest applies.
Spell seeds that require the same type of saving throw and that would be made at essentially the same time combine to use a single save. A subject making saves against a spell with multiple seeds makes no more than one saving throw for each of Fortitude, Reflex, and Will, each of which is used for the effects of all seeds in the spell applying at essentially the same time that require a saving throw of that type. Some special saving throws are always made independently of saves against other seeds' effects, however.
Casting a Spell
A spellcaster can cast any spell that they have access to. Most Arhosan spellcasters can spontaneously create and cast spells as needed, although some create their spells in advance.
Spell Point Cost
Casting a spell requires the spellcaster to expend a number of spell points equal to its cost. A spellcaster cannot cast a spell that would require her to spend more spell points than she has remaining. Spell points are expended at the beginning of casting, and are not recovered if the spell is aborted, disrupted, countered, or otherwise lost.
A spellcaster can only spend up to her caster level in spell points to cast a spell. She cannot cast spells that cost more spell points than that, even if the cost she must pay to cast them is reduced. Some effects modify the number of spell points a spellcaster must spend to cast a spell. Generally, these do not count towards or against this limit (just like cost reductions).
Metamagic
Metamagic feats alter a spell's effects. They must be applied at the time of casting (for spontaneous spellcasters) or at the time of preparation or retrieval (for prepared and retrieved spellcasters), not when the spell is created.
Since Arhosan magic is more fluid than regular magic, it takes more easily to metamagic. Unlike with regular spells, metamagic applied at the time of casting to Arhosan spells does not inherently increase its casting time.
Metamagic usually alters the spell point cost to cast a spell. Unlike most other adjustments, metamagic's effects on a spell's cost apply when determining whether or not the spell costs more than the spellcaster's caster level, and thus whether or not she can cast it.
Components
A spellcaster must provide all of the components of a spell to cast it.
Arcane spells with somatic components are subject to arcane spell failure (usually from armor and shields), as normal.
Concentration
Injury and other distractions can disrupt an Arhosan spellcaster's ability to cast a spell, just like a regular spell.
Counterspelling
Arhosan spells can be used to counterspell each other just like regular spells. Arhosan spells are more fluid, however. The requirements to disrupt one are less stringent, although the process sometimes requires a higher minimum threshold of power. Rather than using the exact same spell, a counterspeller can use any spell containing the exact same spell seeds with an equal or greater cost. The specific details of the two spells, such as their seed type, targeting, or the distribution of power between their component seeds, is irrelevant.
Like with regular spells, several spell seeds have specific exceptions, allowing them to counterspell other Arhosan spells using other spell seeds (or even regular spells).
Multiclassed Spellcasters
Characters with the ability to cast Arhosan spells from multiple sources (whether from class levels, racial abilities, or other sources) track each spellcasting ability separately. Each source of spellcasting has its own pool of spell points, its own spell seeds (or premade spells) known, its own caster level, etc. A spellcaster cannot mix spell seeds known through different sources of spellcasting, nor pay for them with the spell point pool of another source. She may, however, learn the same spell seed multiple times as part of different spellcasting abilities.