Signature Spells
Just as fighters can reach unusual levels of skill by specializing in a particular weapon, a wizard/priest can spend extra weapon proficiency slots in order to specialize in a particular spell. This spell is known as a signature spell. Unlike fighters, who may only specialize in a single weapon, wizards/priests may have one signature spell per spell level, as long as they have the proficiency slots available.
A wizard/priest with a signature spell may still make use of the rest of his spell repertoire normally; he is not limited to just that one spell.
Choosing a Signature Spell
The signature spell must be a spell that the character already knows and is able to cast; a 1st-level wizard couldn’t select fireball as a signature spell, although he could choose an appropriate 1st-level spell from his spell book. If the character is a specialist wizard or priest, he may only select signature spells from the school/sphere of his specialty. Mages and clerics, however, may select signature spells from any school or sphere.
Since specialist wizards/priests must select their signature spells from their own field of study, they find it easier to narrow their specialization down to a single spell.
Learning a Signature Spell
In order for a wizard/priest to gain the skill and practice necessary for a signature spell, he must spend a great deal of time and money, studying every aspect of the enchantment. For all intents and purposes, this is the equivalent of spell research; the character must spend a minimum of two weeks and 1d10 x 100 gp per spell level to master the signature spell and must succeed in a learn spells check to succeed in his studies. If the wizard/priest fails, he still knows how to cast the spell normally, but he can never use it as a signature spell. The character’s proficiency slots are not expended if he fails in his attempt to learn the signature spell. Specialist wizards/priest may apply their spell research bonus to their learn spells roll to develop a signature spell.
Signature Spells in Play
Through hard work and extensive practice, the wizard/priest becomes quite skilled at casting his signature spell. First of all, the wizard/priest casts his signature spell as if he were 2 levels higher for purposes of damage, duration, area of effect, range, and all other level-based characteristics. If the spell has no level-based characteristics (charm person, for instance), the wizard/priest can choose to inflict a saving throw penalty of -2 on the subject’s saving throw when he casts the spell, or he can choose to reduce his casting time by 3.
Secondly, the wizard/priest may memorize one casting of his signature spell at no cost in spells available at that level. In other words, the character gains the specialist wizard benefit of memorizing additional spells. For example, a 1st-level mage may normally memorize one 1st-level spell. If the mage has magic missile as a signature spell, he may memorize one 1st-level spell, plus an additional magic missile, for a total of two 1st-level spells. If the character is a specialist invoker, he can memorize three 1st-level spells: magic missile, a second invocation spell, and the 1st-level spell he normally receives as a 1st-level wizard. Note that the character in this example could choose to spend his discretionary spells to memorize a total of three magic missiles, which wouldn’t be a bad move considering that he’s so good at casting it!
Role-Playing Signature Spells
A wizard/priest with a signature spell often becomes notorious for his use of the spell. Everyone recalls stories of the transmuter who polymorphed folks into frogs, or the fire mage who threw fireballs left and right. The DM should encourage the player to develop his character’s motivations for becoming so skilled with one particular enchantment.