
Eigengrau |
I was thinking of the spell Sepia Snake Sigil and thought about using it along with the spell Blood Money to get around the 500gp cost of making it.
Place it on some kind of "Official looking" scroll and pull it out when harassed by a guard or someone, saying "I've got the Duke's permission right here". Hand it to a guard or whatever and hope he fails his save.
Highly situational of course, but it gives you a fun option of not actually having to kill someone possibly. All depends on if they can read and they're not more powerful than you are and you're not out numbered.
Or just a fun surprise for anyone in your party to find in your belongings, searching around where they shouldn't be.

Kayerloth |
Illusory Script might be doable. The main issue I see with Illusory Script is this portion of the text:
Only the person (or people) designated by you at the time of the casting can read the writing; it's unintelligible to any other character.
Expect some variance in how limited it might become by how specific the GM rules you need to be on the person or people you can designate >> Any official impeding your path vs any Guardsman vs one of the guards working with Sgt Donavan on the 3rd shift of the watch in such and such town. In that respect Sepia Snake Sigil is more "generic", (anyone seeing the protected text), more versatile and potential duration after triggering is days vs 30 minutes or so.
In short both might do the job depending on exactly what you need to have happen. Illusory Script is also relatively subtle, a guardsman reads it and tells all the other guards you check out (and lets you pass) vs a sudden flash and an obvious amber field surrounds the guard hence alerting the other quards etc. etc..

Kayerloth |
*Bah* I read that slightly wrong you don't need to describe the targets only those who can read it without triggering and you ought to be able to describe yourself or the party well enough to satisfy a GM regardless of how detailed they need it to be.
So the big differences will be in duration (both before and after triggering) and the obvious use of SSS vs IS