Addition was an alteration spell that allowed the caster to create one or more simple, ordinary, identical objects or even a single, small, natural creature. This was accomplished by "adding a term to the equation of the moment."
The object created had to be ordinary and non-magical, with a complexity no greater than a crossbow and containing no abstract knowledge (writings or diagrams). The caster was required to describe the object in a single word or short phrase. For example, a priest could create "a block of wood", "a fork", "a longbow", "a footstool", or "a water pitcher", but not "a spellbook" (magical, contains writing), "a blunderbuss" (too technologically advanced), "the crown of Azoun the First" (not ordinary). The caster had no control over design. A water pitcher might be tall, light, and green or short, heavy, and yellow. And unless specified, might be made of wood, metal, or glass, for example.
Objects could not be created inside another object or creature, or appear in a space already occupied by something.
The size and number of objects that could be created, as well as their permanency, was closely tied to the level of the caster. Priests up to tenth level could create one object of up to ten pounds (4.5 kg) which lasted for less than two hours before winking out of existence. Eleventh level priests could create one 20 lb (9 kg) object or four 5 lb (2.3 kg) objects which lasted almost a day or more. Sixteenth level priests could create one 50 lb (22.7 kg) object or ten 5 lb (2.3 kg) permanent objects. And finally, a twentieth level priest could create one 100 lb (45.5 kg) object or ten 10 lb (4.5 kg) permanent objects. All objects created were completely real, non-magical, and could not be dispelled or disbelieved. Multiple objects were identical in every way.
At sixteenth level, a priest using this spell could create one normal, living creature up to 20 lb (9 kg) in weight which would exist for an hour or two and then disappear. The caster had no control over the created animal and its behavior was normal for its species. At twentieth level, a single, normal animal up to 100 lb (45.5kg) could be created and would exist for a few hours.
To cast this spell, the priest had to have a table of numerological formulae inscribed on an ivory plaque, and a silken cord which the priest tied into a complex knot as the incantation proceeded. When the spell completed, the knotted cord flashed out of existence, leaving the plaque behind.