Detect Magic (Greater)

This spell functions as detect magic, except that you can glean much more information from the magical auras that you find, and those auras can be found after a much greater length of time. You can detect a lingering aura for up to %1 days, regardless of the aura's original strength. Additionally, when you use a standard action to concentrate on this spell, you can also study a creature within the spell's area and attempt a Spellcraft check in order to determine the last spell that the creature cast by identifying lingering traces that the spell left in the caster's aura. The DC to identify the spell is equal to 20 + the creature's caster level. Finally, you are able to locate and analyze the signature flourishes in a magical aura that allow you to match a spell to the person who cast it. In order to find these identifiers in a spell's aura, you must spend 1 round focusing on that spell in particular, and succeed at an opposed Knowledge (arcana) check against the caster (or a Knowledge (arcana) check with a DC equal to 15 + the spell level if the caster wants her work to be identified and emphasizes these unique elements rather than obscuring them). Once you learn a caster's set of identifiers, you can remember them as easily as a face or a voice. You can recognize this signature if you succeed at a Spellcraft check when later identifying a spell to determine whether or not that spell was cast by the same individual. The spell greater magic aura can obfuscate this information, making it seem that someone else cast the spell. Greater detect magic grants a saving throw against magic aura (but not greater magic aura).