Ninja, while possessing a magic skill, are not actual practitioners of magic per se: Ninjutsu doesn't attract nearby elementals as other real magic does. Ninjas make use of weapons that can be easily concealed or disguised as common tools. Through intense training they become familiar with these tools, allowing the simplest rope or needle to be used as a deadly weapon. The training and use of these specialized tools is called Ninjutsu (lit. 'the art of stealth'), and a ninja will use them all to defeat his foes.
The category of spells used by Ninja, Ninjutsu, is used to enfeeble or deal damage to enemies, or buff the caster.
The higher your Ninjutsu Skill is, the more effective your spells will be. Ninjutsu damage is calculated as magic damage and is affected by INT and MAB accordingly.