“Sorcery is not a bowl of cherries,” remarks the Man, Myth & Magic rules. The successful casting of a spell is dependent upon overcoming the Fundamental Failure Rate. For “every activity,” (Advanced) MM&M characters have a Fundamental Failure Rate. By default, this rate is 50%; meaning “you will have to throw 50 or better on the percentile dice to score a hit [or otherwise succeed].” (I know, that's a 49% chance for failure. What difference does a single percentage point make? A great deal actually; read on.) Circumstances can modify the Fundamental Failure Rate. For example, a warrior's SKILL characteristic affects his or her Fundamental Failure Rate for striking a foe in combat. According to page 12 of Book II:
For every 10 SKILL points above 50, subtract 1 from your basic 50 needed to hit. For every 10 SKILL points below 50, add 1 to the score you need to hit.So, a warrior with a SKILL value of 40 would succeed in a combat strike by throwing 51 or better. The rules would have been better served by having a Fundamental Success Rate instead of a Fundamental Failure Rate. High SKILL values increasing success rate with low values decreasing success rate is a more intuitive concept.
The rules explaining the Fundamental Failure Rate and how it is affected by SKILL are provided in the (Advanced) Combat section. Evidently, these rules are meant to be extrapolated to 'Prime Abilities' other than combat. Each class has a Primary Ability; for warrior-type classes, it is combat. The African Witch-Doctor, Egyptian Sorcerer, Hebrew Sorcerer, Oriental Shaman, and Hibernian Leprechaun all have 'magic' as their Primary Ability. As such, they are capable of casting all of the spells in the Grimoire. Each of these classes also has a set of spells exclusive to that class. Other classes (e.g., Sibyl, Priest) have “spells,” but these are considered to be psychic or divine powers and such classes do not have access to the Grimoire spells. There are 37 distinct character class/nationality combinations in the standard (AD 41) MM&M setting, so only about one character in six will have Grimoire spells. The ratio is even less in the ancient (1375 BC) setting, with 43 distinct character combinations and only three of which have a 'magic' Primary Ability. (The Shaman and Leprechaun classes are not available.)
For (Grimoire) spells users, the Fundamental Failure Rate can be altered by both SKILL and INTELLIGENCE. Assuming ±1 per ten points above/below a value of fifty, there is – at most – a mere 19% difference in the Fundamental Failure Rate between the smartest, most competent spell caster and the dumbest, least competent spell caster. Thus, a single percentage point becomes significant.
Each spell has a 'casting cost' in POWER points; the points are spent whether or not the casting roll is successful. Of course characters (not just spell casters) can increase their chances of success (for one roll) by 1% per ten POWER points spent. Additionally, for 250 (permanent) POWER points, a character may increase a characteristic value by one point. Given that reincarnation costs 200 POWER and that characteristic values will be redetermined as part of reincarnation, this may not be a wise investment.
According to the rules, “if you are using a spell which takes effect at a distance, there is no immediate way of discovering whether or not it was effective.” This suggests that the Lore Master makes all spell casting rolls. However, for all but two of the Grimoire spells, the maximum distance at which a spell can take effect is fifty feet.
Any gold pieces within fifty yards of the caster will mumble “Here I am” upon the successful casting of Gold Sniffer (10 POWER). The same thing happens with Treasure Finder (15 POWER) except gems speak, not gold pieces. With Lie Detector (10 POWER), the caster may “detect falsehood in any one given statement.” Does “statement” mean one item of information? One sentence? How does one target a “statement”? Is it retro-active?
Any “mortal human or beast” must succeed with a COURAGE roll in order to travel through a Circle of Fear (10 POWER per 20' radius). Web (25 POWER) causes “a 10 ft. diameter vertical web” to come into being. Assuming the the web is placed over an opening of less that ten feet in diameter, “mortal humans and animals” will not be able to pass (until the next segment). Pathfinder (15 POWER) allows the caster “to retrace steps in any terrain.” With Freeze (30 POWER), the caster paralyzes a target for the remainder of the segment.
Poltergeist (30 POWER) causes “an invisible imp” to come into being. It “can throw small objects and set fire to easily burned materials.” On any given turn, there is a 50% chance that the imp “will obey the caster's wishes.” I suppose that means “obey the caster's wishes” to the extent the imp is able. I also suppose that the caster must vocally command the imp, but I could be wrong. Speaking of invisibility, the caster may cause “any object he may hold in his hands” to become invisible with a successful casting of Invisible Object (40 POWER). A caster “may make himself invisible” with Invisibility (85 POWER), the most expensive of the Grimoire spells in terms of base POWER cost. Note that the caster's clothing and accoutrements are not rendered invisible with this spell.
A Zone of Purity (40 POWER) is a 20' diameter circle in which “no spells may be cast until the end of the segment.” Of course, spells already in effect remain unabated. To stop an existing spell, the caster must successfully cast Terminate within twenty-five feet of where the effects of the target spell manifest. The POWER cost is equal to the target spell's POWER cost, but in no instance may it be less than 10 POWER.
A successful Curse spell “causes magical weapons and artifacts to lose their magical properties” permanently. The POWER cost of the Curse spell is equal to the POWER cost of the target object's enchantment (which, of course, the caster may not necessarily know). If the caster does not have enough POWER to cover the cost, “the balance is taken from him in Life Points at a ratio of 3 Life Points for each POWER Point.” For reference purposes, a harp that plays by itself costs an Egyptian Apothecary 25 POWER Points to create while a 'Blessed Bow' (-10 THN) costs an Oriental Shaman 100 POWER Points to create.