The philosophy of the Sphere of Numbers holds that the structure of reality—the "equation of the moment"--can be analyzed and modified by someone with sufficient knowledge and power. The addition spell allows a priest to add a new mathematical term to the equation of the moment. This effectively allows a new object or even a living creature to be brought into existence temporarily.
The effect of this spell varies depending on the level of the caster. At 10th level or lower, addition can create a single, inanimate object weighing up to 10 pounds. The spell gives the priest only rudimentary control over the creation process, so the object cannot be complex. The object must be described in a single word or short phrase (e.g., "a water pitcher" or "a block of stone"). The caster has no control over elements such as shape or color; thus, the water pitcher might be short, squat, and blue, or tall, slender, and red.
Objects created with this spell cannot be of any greater mechanical complexity or technological level than a crossbow. If the priest tries to create an object that breaks this prohibition, the spell fails and nothing is created. Thus, if the priest tried to create "a pistol," assuming he had heard the word somewhere, the spell would fail.
Objects cannot contain any information in an abstract form such as writing or diagrams. If the priest tries to create an object that breaks this prohibition, there are two possible results: the spell may fail, or the object may be created without the information.
Thus, if the priest were to attempt to create "a spellbook," the result would be either a book similar to a spellbook with blank pages, or nothing at all.
The object appears at whatever location the caster wills, as long as it is within spell range. The object cannot appear in the same space occupied by another object or creature, or within a hollow object (for example, the priest cannot create an object blocking the trachea of an enemy).
The object created by addition remains in existence for 1 turn per level of the caster.
During this time, it obeys all the laws of physics as if it were a "real" object. The object cannot be disbelieved and spells such as true seeing cannot distinguish it from a naturally-occurring object.
Priests of 11th to 15th level can create a single inanimate object of up to 20 pounds in mass or two identical objects, each of up to five pounds in mass. The object(s) so created remains in existence for two hours (12 turns) per level of the caster.
Priests of 16th to 19th level can create a single inanimate object of up to 50 pounds in mass or up to 10 identical objects, each of up to five pounds in mass. The object(s) is permanent unless destroyed. Since these objects are not magical constructs, but real additions to the "equation of the moment," dispel magic has no effect on them.
Alternatively, the caster can create a single normal (nonmonstrous) living creature of up to 20 pounds in weight. The creature, once created, behaves as a normal member of its species; the caster has no control over its actions. This creature remains in existence for 5 rounds per level of the caster.
Priests of 20th level and above can create a single inanimate object of up to 100 pounds in mass or up to 10 identical objects, each of up to 10 pounds in mass. The object(s) are permanent. Alternatively, the caster can create a single normal (nonmonstrous) living creature of up to 100 pounds in weight and up to 2 hit dice. The creature, once created, behaves as a normal member of its species; the caster has no control over its actions. This creature remains in existence for 2 turns per level of the caster.
The material component is a small table of numerological formulae inscribed on an ivory plaque, plus a length of silken cord. During the casting, the priest ties the cord into a complex knot. As the magical energy is discharged, the cord vanishes in a flash of light.
The plaque is not consumed in the casting.