Lesser Invisibility

This is an arcane spell available to many casters, considered somewhat common in magical circles, allowing for limited invisibility.   This is a spell available to Kipilu of Tezitkal.   Lesser Invisibility allows for one creature to become invisible for an hour. This spell ends early if the invisible creature engages in a violent action or casts a spell. The caster of this spell must sustain the spell through active effort, meaning it can be disrupted early.   Interestingly, the spell seems to factor in the invisible creature's intent to define 'violence' - it cannot be tricked by "spilling" acid or "gently stabbing". It seems to tolerate theft and other non-violent acts, though. Only a few magical centers of knowledge have fully experimented with this spell's limits.   A "greater Invisibility" spell does exist that disables this no-violence and no-magic limiting mechanism, but it is much more challenging and taxing.    Powerful governments and major institutions know and prepare for this spell. Many of these mix in Prism guards, whose echolocation can pierce this spell's effect when they get close enough. Agencies devoted to espionage are particularly careful in preparing for and using this spell.