These rules assume as a basis Ars Magica, 4th Edition. You will need a copy of that book or Ars Magica, 3rd Edition, in order to make complete sense of these rules. The combat skills are based on 4th Edition, while the Passions are based on 3rd; most everything else is close enough between the two as to make no significant difference. Also, you will need a copy of either the AD&D 2nd Edition Player's Handbook or the D&D 3rd Edition Player's Handbook, principally for spell and equipment lists.
The eight characteristics are Intelligence (Int), Perception (Per), Strength (Str), Stamina (Sta), Presence (Pre), Communication (Com), Dexterity (Dex), and Quickness (Qui). The pairs are Int & Per, Str & Sta, Pre & Com, and Dex & Qui. If you are coming to this from D&D, Str and Int are roughly equivalent to Strength and Intelligence, respectively. Sta is essentially the same as Constitution, and Pre is very close to Charisma, encompassing both appearance and behavior. Dex encompasses hand-eye coordination and fine motor control, while Qui is reaction time and bodily speed together they are equivalent to Dexterity. Comm is exactly what the name suggests, and is part of Charisma in D&D. Per is a combination of the ability to notice things and intuition. Int is the most important characteristic for wizardly spellcasters. Per fulfills a similar role for priests, but is not quite as important. Both will also do well to have high Comm, and Priests can use lots of Pre while wizards need some Dex and some Sta. Rogues should have high Dex and Per, and Qui if they're the burgling sort or Pre if they're the swindling sort. Warriors need strong Sta, Dex, and Qui, and high Str will always come in handy. Bards need Pre & Comm principally, but Dex and Per are almost as important. Psionics utilize Int and Per about equally, and need Sta to have any staying power.
There are two ways you can generate characteristics. The first is to roll the difference of 2d10 (generating a number from -9 to +9) four times. If the total of all four rolls is less than 0, you may reroll them all. Then assign one of the results to each of the pairs, as you desire. The sum of the two characteristics in that pair must equal that result, and neither may be greater than +5 or less than -5. The other method involves spending points. Use the Skill Point Costs chart to purchase your characteristics. You start out with 7 points to spend and can get more by taking equivalent negative points. Again, no characteristic may be greater than +5 or less than -5.
There are two ways to improve your attributes. Through play and with experience (exp). Some attributes can only be improved in one way or the other.
All Abilities can be improved with exp. The cost to go up one level is equal to the new level. i.e., to go from a score of 6 in an ability to a score of 7 would require 7 exp.
Talents can not be learned/taught.
Skills can be taught, but not learned: you must have a teacher, not just a textbook or example. Teacher's score/student's score = levels of skill gained (up to 3). This still costs exp, but at the rate appropriate for the number of levels gained, rather than the particular levels themselves. I.e., a warrior with Single Weapon (12) teaches one with Single Weapon (3). He could gain up to 3 points [the maximum, since 12÷3 > 3] at a cost of 6 exp [score of 3 on the Skill Point Costs chart], but since he has only 4 exp to spend, his new score is Single Weapon (5), which costs him 3 exp [the cost of a score of 2, the difference between the old score and the new].
Knowledges can be learned or taught, as per the rules: teaching source/current level = points gained (up to 5). This costs no XP.
Scores that can not be improved with Experience:
Roll Technique + Form + Int ≥ Spell Level
Halve total roll for spontaneous effects
You must achieve the level of the spell with your roll.
Spell levels are 10 x AD&D level
Spontaneous spells always burn one Fatigue.
Formulaic spells only burn Fatigue if the level exceeds twice Technique + Form + Stamina; then they also cost one Fatigue.
Range: how far away the center of the spell is. Many spells still originate with the caster - see Targeting, below. Factors in Range that are dependent on caster level use the caster's Power score. Having an Arcane Connection to the target reduces the effective range to the target. Touch becames Self; Distance and Eye Contact become Touch; Planar and Infinite become the distance to the Arcane Connection itself.
Self: Only the spellcaster him- or herself.
Touch: Any being or object that the caster physically touches.
Eye Contact: The caster must actually make eye contact with the subject.
Distance: A particular distance, usually in yards, as stated in the description.
Planar: Not actually infinite, but limited only by the bounds of magic. A magical spell can not cross the boundary of a Crystal Sphere, and can not cross planar boundaries (except the Border Ethereal) without magical help.
Infinite: Still not able to cross the boundary of a Crystal Sphere, but able to cross planar boundaries.
Target: Use Finesse to determine targetting.
Targets are (see 3rd ed):
Duration: Use Power to determine variable durations.
Components: all spells require one or more components to activate them. These must be employed, unless you have the Silent Magic or Subtle Magic Virtues.
Verbal: caster must be able to speak freely
Somatic: caster must have free use of both arms
Material: the required objects/substances must be present. Unless otherwise stated, they are destroyed during the casting (even if unsuccessful).
Overcoming other magic:
Add your Penetration to the total casting roll, and compare to the Magic Resistance, or other defense. Also, if the effect of a spell is dependent on Power ("caster level"), these two attributes are each others' requisites. In other words, you use the lower of Penetration and Power for both overcoming magic resistance and determing damage, etc., in the situation where both are required.
Roll Realm + Faith ≥ Spell level
Halve roll if it's effect/method is governed by a lesser sphere of the god
Spell level = 10 x AD&D Spell level
Use Understanding talent for "caster level" to determine range, damage, etc, and for fine control.
Penetration, for overcoming other's magic, is equal to Faith x5.
True Faith effects:
Calling Miracle: Roll Quality Die < True Faith ± Passion(s)
Turning Undead: Roll 10 x True Faith ≥ Might of Undead
Must have Insight score.
5 Disciplines, access to each is purchased separately. Within the Disciplines there are a number of powers. Access to a Discipline gives you access to all of its powers, purchased just like other abilities.
Roll Focus + Power + Insight ≥ Effect Difficulty
Power can take effect at any level up to the result of the roll, at the user's discretion.
Effects up to the score of that Power cost no Psychic Reserve. Effects up to twice the score in that Power cost 1 Psychic Reserve. Effects up to 3x the score in that Power cost 2 Psychic Reserve. And so on. If you run out of Psychic Reserve, you can use Fatigue Levels on a 1-for-1 basis.
Psychic Reserve = Insight x5 + Presence + Stamina + Intelligence
Psychic Reserve is regenerated at a rate dependent on your Focus score. During normal, non-strenuous activity, you regain as many points as your Focus score, per day. During sleep or meditation, you regain as many points as your Focus score, per hour. You can not regain Psychic Reserve while engaged in any activity that would require Fatigue rolls.
Maintaining, penetration, combat:
Use Concentration to maintain a power.
Use Focus to overcome psychic resistance.
Use Psychic Attack/Psychic Defense to fight psionicly.
For each Wound Level of damage: double die roll, but roll one extra Botch die. Don't lose Fatigue Levels.
Use the lowest Convergence score of all the converging psionicists. This is the minimum convergence. This number times the number of psionicists involved is the convergence total.
All Power scores are limited by the minimum convergence.
The convergence total replaces Focus in all rolls.
Roll Quality Die < Purity
Execute Martial Arts Maneouvers:
Roll Purity + Characteristic ≥ Maneouver Level
Martial Arts Paths:
|Offensive Power||Arcane Magic||Divine Magic||True Faith||Psionics||Purity||Faerie||Inner-Planar||Outer-Planar|
fighting in water
fighting in rain/wind
fighting in mud
fighting on horseback
fighting in zero-G
fighting in the dark
fighting multiple opponents
fighting while outflanked
fighting while prone
fighting vs. particular weapon(s)
fighting against someone on the high ground
fighting on uneven/uncertain ground
fighting vs. mounted opponents
fighting underwater/while swimming
fighting while bound
making multiple attacks
3: First Missiles
5: Second Missiles