Random musings from me on a system using the domain power to determine realm magic caster level rather than the character levels of the regent.
Domain caster level :
Base: Domain Power/7
Regent:
Bloodline strength: Caster level:
Minor +1
Major +2
Great +3
True +4
Vorynn bloodline +1 (Arcane only)
Reynir bloodline +1 (Primordial only)
Examples:
For the premier temples of Anuire with a domain power in the region of 60, plus a regent with a major bloodline, total domain caster level would be 60/7 + 2 = 12. This allows realms spells of up to level 5, but will be limited in effect based on regency generation.
For more regional temples, with domain power of at least 35, plus a regent with a minor bloodline, total domain caster level would be 35/7 + 1 = 6. This allows realm spells of up to level 3, allowing the majority of the utility spells, but limiting any high magic effects.
Other factors:
Court: Court size does not provide any impact on domain caster level. Large courts do however provide additional court actions, usable for preparing realm spells as a realm action.
Bloodline score: Additional bloodline strength allows for increased RP gain each turn, allowing a greater number or more powerful spells to be cast.
Blood abilities: Certain blood abilities can
Vassals: Domains having vassals do not gain any advantage on caster level, but loss of domain power and associated spells
Lieutenants: Lieutenants do not affect caster level, but provides actions that can be used for preparing spells, research etc.
Missing regents: If the regent is missing or incapacitated, the remainder of the domain can use the court to cast spells at half the domain power.
Structures: Normal structures have no effect on domain caster level. Structures enabling a larger court will indirectly benefit domain. Some unique structures and domain special rules can affect domain caster level, or effective domain caster level for certain spells.
Character levels/feats/abilities: The statistics of individual characters making up a domain (other than those listed above) does not affect the domain caster level or casting of realm magic.
Magic type:
Each domain can only cast realm magic spells of one type; determined by their court type. For domains with Court[Covenant], Court[Temple] or Court[Grove] use arcane, divine and primordial magic respectively, while domains with Court[Noble] or Court[Guild] are unable to cast realm magic.
Spells known:
Spells known are based on the entire domain, and not limited to the regent. Even if the regent dies, the known spells are retained.
Additional spells can be acquired by a domain through research actions.
If the domain caster level drops below that required to cast a spell, the spell remains known, but not possible to prepare until the temple regains its former glory. Any spells three levels higher than that permitted by current domain caster level will be lost. Regaining lost spells can possibly be easier at DM’s discretion.
Spell slots:
One spell can be prepared per allowed spell level. Each spell slot can only be used once per turn.
One additional spell per level can be prepared, but domain must pay a number of RP when preparing spell equal to twice spell level.
A third spell per level can be prepared, but RP cost is four time spell level.
Variants:
Domain power divisor can easily be changed depending on level of magic desired in campaign. A lower value, such as 5, provides for a much larger number of high levels spells that can be expected to be available. A divisor of 10 will provide with a much more low-magic campaign, making even 5th level spells a rarity at best.
[Example: For a very large temple in a high magic campaign, a domain power of 100 would give the maximum domain caster level of 20 (100/5 = 20).]
Cooperative casting: Several domains can all concentrate their efforts to call on great powers that the individual temples. Total caster level based on adding parts of domain power of the additional temples to that of the primary caster. Only bloodline strength of primary caster affects final domain caster level. (Primary caster does not have to be domain with highest power, and will likely be a political decision.)
Second temple: +50%
Third temple: +35%
Fourth temple: +20%
Fifth or more: +10%
[Example: Four temples have joined forces to strike back at the forces of the shadow that have crossed through the veil. Four temples of domain power 60, 50, 40 and 30 combine their efforts. They are being led by the regent of the temple with domain power 50, who has a major bloodline. Total domain caster score is {50 + 60x0.5 + 40x0.35 + 30x0.20}/7 + 2 = 16. This allows the combined temples to cast Banish Army (which is known by the domain of the primary caster).]
Court limitation: Maximum realm spell level possible to cast is limited to effective court level of domain.
Multiclass domains: Certain domain are allowed a secondary magic type, with separate rules for calculating the domain caster level of each type of magic.
