Ars Magica - System

System

The game system is based on the d10. When an action is performed, one of the character's eight attributes is added to the relevant skill, and a d10 is rolled. The total of attribute + skill + d10 is compared to a target difficulty. The action succeeds if the rolled total is greater than or equal to the difficulty.

If the action can only result in a simple success or failure, the die roll of 1-10 is merely added to the total (called a "Simple roll"). If there is opportunity for exceptional success or failure, it's called a "Stress" roll. On a Stress roll, results of "1" and "0" have special meanings: a ONE is rerolled, and the result doubled (additional "1"s lead to successive doublings: quadrupling, octupling, etc; the final non-"1" being enlarged by the multiplier); a ZERO is treated as a zero (rather than a ten), AND one or more additional d10 botch dice are rolled. If any of these botch dice show a zero, the character has botched - failed in some disastrous way; if none of the botch dice turn up zeroes, then the die-roll is treated as a zero. Assuming the roll didn't botch, the total is (as above) compared to the difficulty of the action to determine success or failure (and the degree of success or failure).

The focus of the game is the magic system. There are 15 Arts divided into 5 Techniques and 10 Forms. The Techniques are what one does and the Forms are the objects one does it to or with. This is sometimes called a "Verb/Noun" magic-system. The Arts are named in Latin.

The Techniques are named after the corresponding first-person singular present tense indicative mood Latin verb.

• Creo is the technique that lets the Magus create from nothingness, or make something a more "perfect" examplar of its kind; this includes healing as healed bodies are "more perfect" than wounded bodies.
• Intellego lets the Magus perceive or understand.
• Muto lets the Magus change the basic characteristics of something, giving something capabilities or properties not naturally associated with its kind.
• Perdo lets the Magus destroy, deteriorate, make something age and other similar effects - essentially, making something a worse example of its kind.
• Rego lets the Magus control or manipulate something without affecting its basic characteristics.

The Forms are named after the corresponding singular accusative Latin noun.

• Animal is used for animals. Since bacteria were unknown in medieval times, illnesses are evil spirits, which come under Vim.
• Auram is used for anything that has to do with the air, including lightning. Weather phenomena such as rain and hail may be covered by Auram or Aquam.
• Aquam is used for water, or any other liquid. This includes ice in the 5th edition; In 4th edition, Ice was Terram, since it is a solid.
• Corpus (the incorrect declension Corporem was used in older editions) is used for the human body.
• Herbam is used for plants and fungi, and their products - cotton, wood, flour, etc.
• Ignem is used for fire, and fire's basic effects of light and heat.
• Imaginem deals with images, sounds, and other senses, though humans' ability to perceive them is part of Mentem.
• Mentem deals with intelligence and the mind, such as human or ghosts. The minds of animals are not affected by Mentem but by Animal.
• Terram stands for earth and minerals, or any other non-living solid.
• Vim has to do with pure magic; many spells to ban or control demons and other supernatural beings also belong to this Art, as such beings often have a form that expresses magically.

Thus, Creo Ignem spells create fire (or light, or warmth); a Perdo Ignem spell may quench a fire, create darkness, or drop the temperature in a room. A typical Perdo Imaginem spell is granting invisibility to the caster by making one's image disappear. Rego Aquam could turn water into an unusual, but natural form (e.g. creating a pillar of water), while Muto Aquam could turn water into, for example, oil or wine; or change the nature of water so that it's murky and green but still healthy to drink. An Intellego Mentem spell may permit the caster to understand any language, or to read minds; and so on... A mage's skill when casting a spell is the sum of their scores in the appropriate technique and form.

If a spell involves more than one technique, or more than one form, this is known as a requisite . The lowest technique score and the lowest form score are used, as they are taken to be the limiting factors on the caster's magical knowledge. For example, a spell to turn a person into a stone statue would involve Muto + Corpus or Terram; The player would add the character's Technique (Muto) score to the lower of their Form (Corpus and Terram) scores to determine their casting total for the spell.

By combining these techniques and forms, the Magus may achieve any effect and spontaneously cast a spell with that desired effect. However, there are often severe limits to the level of power a Magus can generate by casting spontaneously, and so he may also choose to learn a "formulaic" spell with that desired effect. A Magus is further limited in terms of the spell's application: Ars Magica features a set of magical 'laws', similar in concept to those of physics, defining the upper limits of any magical spell (Creo Corpus, for example, cannot create 'true' life, nor can it restore the dead; magic, in general, cannot affect the flow of time, nor can it affect the 'lunar sphere or anything above it' (i.e. the realms of the Divine, according to medieval thought)).

Magic is treated in this game-system as a serious object of study: Magi are supposed to spend a long time in their laboratories: preparing new spells, studying their Arts, creating magic-items, etc. The game system provides rules for magical research on a timescale of 3-month seasons.

These seasonal activities usually concern learning or lab projects, and are most important for Magi. Although participating in stories awards you Story Experience, the real progress and advancement in the Ars Magica system is from these seasonal activities. Hence, the flow of time is this game system is most often a lot faster than in other RPGs, since player characters primarily advance in the down time between adventures. To accommodate this, the system is geared for such a flow of time, allowing the Magi to prolong their lives with Longevity. Secondary characters are meant to come and go, eventually dying in action or even living to retirement, while the Magi carry on.

Learning is mostly done using books to Study from. Every Covenant will have a respectable library, since the magical tradition of the Order of Hermes is a bookish one. One can also learn from Teaching or Training if you can find a suitably skilled individual, or one may Practice by one's self. Magi who are able to write useful books or teach well can use these as commodities, trading with other magi for books or training. Finally, a one may learn from Exposure while working a trade or performing lab activities. This is the least efficient way to learn, but it is a nice side benefit to the result of the work done.

Lab Projects concern magical projects to enhance your repertoire of spells or magical artifacts. The basic mechanics for this are more or less the same for all activities. All projects have a Level of Effect to which you compare your Lab Total. Lab Totals are calculated as the magus' Intelligence + Magic Theory ability + sum of a Form and Technique + other bonuses. Other bonuses may be from local Aura, quality and specialization of lab, assistants, previous knowledge, sympathetic connections from items, or in rare circumstances another ability. Some activities merely require your Lab Total to match the Level of Effect, but mostly you accumulate points towards finishing the project each season. For each point by which your Lab Total exceeds the Level of Effect, you accumulate one point towards the total Level. Thus a Lab Total double the Level of Effect allows you to complete the project in a single season.

The following Lab Projects are among the most basic ones:

• Invent Spells. The magus invents a new magical effect from scratch. Inventing a variation of a known spell is easier than a completely new one. These Formulaic Spells are somewhat rigid in their definitions, but are more powerful than the more flexible Spontaneous Magic.
• Enchant Device. The magus may create a magical artifact which may hold a magical effect like those of Spells. These can be used by anyone, not just magi, and do not suffer the usual modifiers to casting which spells do. Usually these cost vis to make, but the Lab Total gets a bonus based on the sympathetic Shape & Material bonus of the material used. E.g. a staff gives a bonus to enchant effects that control things at a distance. They can be made as Charged Devices (which cost no vis but have a limited number of uses), Lesser Devices (which require the magus to be able to enchant them in a single season, and may only hold one effect), or Invested Devices (which require that the magus spends additional time to prepare in advance, may be enchanted over several seasons, and may hold several effects based on the size and material).
• Enchant Talisman. A Talisman is a special and personalized form of Invested Device, with many additional features. Talismans have a much higher capacity for the number of effects with which they may be enchanted, and are easy to enchant. Furthermore, the magus may attune some or all of the Shape & Material bonus the item has, and the bonus for his spellcasting. Should a Talisman fall into the wrong hands, it would leave the magus very vulnerable.
• Longevity Ritual. A Creo Corpus effect that prolongs the magus' life by granting him bonus for Aging Rolls, making it more likely that he will avoid crippling effects of age until late in life. Magi may very well live to be 200 years old, or more barring other mishaps. Magi often pay specialist magi to perform this for them, to get the best ritual they can afford.
• Bond with Familiar. The magus may find and attract an animal - magical preferably - with which he connects somehow. Usually this will be an animal which thematically is in synch with the magus' personality and magical arts. An Auram magus might bond with a bird, while a Herbam magus might find a squirrel. The Bonding process is long and hard, but may very well be worth the effort. The animal learns to communicate with the owner, and while it does not become intelligent per se, it is more enlightened than a normal animal of its type. One boon is that the Familiar might be enchanted with almost limitless amounts of enchantments, with a few restrictions about what the enchantments can affect and who activates them. But the primary benefits are from the Bond Scores: the Gold Cord concerns magic, and helps the magus avoid magical botches. The Silver Cord concerns the mind and helps the magus against mental effects among others. The Bronze Cord concerns the physical connection and helps the magus be more enduring and tough. The better Lab Total the magus can muster, the better Cord score he will forge.