For the occultist circles abilities:
Once completed, this circle functions as a permanent magic circle against any alignment of the occultist's choosing. The circle can't be against a component of the occultist's alignment (if he is lawful good, for example, it can't be a magic circle against good or law). The circle remains until its form is physically broken (for example, if the lines are smeared or the salt is scattered). Only a living creature can break the circle; environmental effects can't break it.
This guide suggests:
However, it does have one small advantage over normal circles, in that the creature that wishes to break it must be living. This makes it very good at keeping undead at bay. Horde of zombies on the way? Toss down a magic circle and then just shoot them from inside.
By "breaking the circle" does that mean making it nonfunctional or does that mean crossing over? My first read was "only a living creature can ruin a circle", thus undead could cross over it willy and/or nilly, but the guide I found (linked above) has a different interpretation. I couldn't find anything else in my searches that broached the topic, so I thought I'd just ask.
Thanks!
As a magical circle does nothing to prevent creatures from entering unless they are summoned, your interpretation is the correct one. Mentioning the enviromental effects wouldn't make sense otherwise.
I think the author confused two things. He seems to think the circle is a physical barrier against evil creatures, but that's only against evil summoned creatures. Zombies and the like will have no problem crossing that circle.
By "breaking the circle" I'd think it's actually destroying the circle, not just crossing it.
At 8th level, an occultist learns how to draw magic circles. To draw a circle, he must have chalk, salt, blood, powdered silver, or some other appropriate substance at hand (although he can press a magic circle into a softer surface such as dirt or clay). Drawing a circle takes 1 minute and requires the occultist to expend 1 point of mental focus (either generic focus or focus from any one of his implements). Once completed, this circle functions as a permanent magic circle against any alignment of the occultist's choosing. The circle can't be against a component of the occultist's alignment (if he is lawful good, for example, it can't be a magic circle against good or law). The circle remains until its form is physically broken (for example, if the lines are smeared or the salt is scattered).
Only a living creature can break the circle; environmental effects can't break it. An occultist can have only one circle created in this way at a time. If he creates a second circle, the first one loses all its magic powers. This type of magic circle can't normally be focused inward to bind an outsider.
The first bolded part is still kinda ambiguous, but the part in brackets gives examples of how to break it. Lines smearing is a way of breaking it, but not walking across the line.
I also think the author was a little fast and lose with wording.
"Only a living creature can break the circle; environmental effects can't break it." doesn't actually mean an undead can't break the circle IMO. It's bad wording from the writer who wasn't thinking about it. They were trying to convey creatures break it on purpose, it's not accidentally broken by the weather. But what they intended and what they actually wrote are different.
But considering it's supposed to work like a regular magic circle against alignment X, but permanently, undead shouldn't have a problem wrecking it.
Of course undead don't really care about that either since you don't summon undead (I don't think there are any undead on the summon list) they can just walk through the magic circle no problem.