(I won't go into detailed descriptions of rule mechanics because they're identical to the rules for technological development presented in Aria Worlds. If you don't have Aria Worlds yet, you should seriously consider buying a copy; it's a very worthwhile investment. (So, Christian, when do I get my check? ;) )
Magical development, like technological development, is described by a set of 7 values. These 7 values are averaged to obtain the overall Magic Value of the society or Omni. The values are: Power, Change, Control, Creation, Illusion, Knowledge, and Mind. Like the Dominant Materials Value for conventional technology, the Power Value serves as the upper limit for the other 6 values. Rates of Advancement and Assimilation are determined as for technology, though I would suggest raising the Rate of Assimilation (ie, slowing the process) unless the workings of magic are fairly obvious.
I considered adding a mechanic to reduce the effectiveness of magic as conventional techologies develop (reflecting a loss of belief in magic as science advances), but decided against it. I was working along the lines of reducing Power Value by 1 for every n points of technological development (all other areas of magical development could suffer the same loss or only those in excess of the new Power Value; all losses could be regained normally). Another possibility would be to put a cap on the sum of Magic and Tech Values.
Before presenting the tables for the capabilities resulting from each level of magical development in each area, I'll present some basic (and relevant) details of the Origin which this system is being used with.
The world in question is inhabited by several sentient races, each of which has a unique relationship with magic. The in game terms, each race has different Access Facilities and Casting Methods. As a result, members of one race may only benefit from the magical knowledge of other races on very broad, theoretical levels. (There is one exception, Akie, which I'll go into in at another time.)
The Origin may produce any effect (all Archetypes and Dominions are rated at 5) within the limits of the available magical development.
No Temper Aspects or Resistance are initially available, but they can be gained as a result of increasing magical development.
Spellcasting within the Origin requires an Insight Trial to avoid Omnessence waste. The Difficulty of the Trial is a base 7, reduced by (Power Value)/4, always rounded against the Adept's favor. If the Trial fails, each Degree of Failure increases the spell's Omnessence cost by 1 (this is purely waste energy; Might values are not affected). If the Omnessence waste causes the spell's cost to exceed the Adept's available Omnessence, the spell does not take place and all Omnessence spent on it is lost.
(Christian: Is there any 'official' way to determine Insight? Aura is based off Empathy and Faith is bought up from 0, but I haven't found anything on determining Insight...)
Now for the tables: (All descriptions of effect types are taken directly from the Potency/Intricacy table on MG 139-140.)
At any PV, the maximum Effect Might for spells = PV.
Value Description 1 Must Memorize Solidified Paradigms 2 Alter Potency/Intricacy Temper Aspect 3 Counter Resistance at +4 on Effects Trial, spontaneous spells available 4 Participation with Principal, Extend Temper Aspect 5 Widen Temper Aspect 6 7 Counter Resistance at +3 on Effects Trial 8 9 Co-equal Participation, Invited Temper Aspect 10 11 Counter Resistance at +2 on Effects Trial 12 Overpower Temper Aspect 13 14 Alter Resistance 15 16 Counter Resistance at +1 on Effects Trial 17 18 Contagious Temper Aspect 19 20 Absorb Resistance
Value Description 1 Nature of Change: Slight, Energy: Slight 2 Size: Slight 3 4 Energy: Moderate 5 Size: Moderate 6 Nature of Change: Moderate 7 Energy: Impressive 8 9 Size: Impressive 10 Nature of Change: Impressive 11 12 13 Size: Epic 14 15 Nature of Change: Epic 16 17 Size: Mythic 18 19 20 Nature of Change: Mythic
Value Description 1 Target Temper Aspect, Targeting at +3 Difficulty 2 Targeting at +2 Difficulty 3 Delay Temper Aspect 4 Penetration: Moderate 5 Sophistication Temper Aspect, Targeting at +1 Difficulty 6 Build Temper Aspect 7 Targeting at Base Difficulty 8 Removed Temper Aspect, Penetration: Impressive 9 10 Mechanism Temper Aspect 11 Chain Temper Aspect 12 Penetration: Epic 13 14 15 Targeting at -1 Difficulty 16 17 Penetration: Mythic 18 19 Targeting at -2 Difficulty 20 No Passive Resistance Temper Aspect
Value Description 1 Restoration: Slight 2 3 Maintain Temper Aspect 4 Creation: Slight 5 Restoration: Moderate 6 7 Imbed Temper Aspect 8 Creation: Moderate 9 Restoration: Impressive 10 11 Restoration: Epic 12 Anchor Temper Aspect, Creation: Impressive 13 14 Restoration: Mythic 15 16 17 Creation: Epic 18 19 Creation: Mythic 20 Permanence Temper Aspect
Value Description 1 Slight Image, Slight Effect 2 3 Moderate Effect 4 5 6 7 Impressive Effect 8 Moderate Image 9 10 11 12 Epic Effect 13 14 15 16 17 Mythic Effect 18 19 20 Impressive Image
Value Description 1 Familiar target, Thought-based Effects, Slight Contact 2 3 4 5 Moderate Contact 6 Unfamiliar target 7 Moderate target element 8 1 Physical Effect 9 Impressive Contact 10 11 2 Physical Effects 12 Impressive target element 13 Epic Contact 14 3 Physical Effects 15 16 17 4 Physical Effects 18 Epic target element 19 20 5 Physical Effects, Mythic Contact
Value Description 1 2 Fundamental Inertia: Slight 3 4 5 Fundamental Inertia: Moderate 6 7 8 9 10 11 Fundamental Inertia: Impressive 12 13 14 15 Fundamental Inertia: Epic 16 17 18 19 20 Fundamental Inertia: Mythic