Pathfinder: Magic Circle against Evil against a spectre or ghost

[Scottlang]

I have a player cast Magic Circle against Evil when a spectre attacked, and he was under the impression that the spectre was an evil outsider or summoned creature entery for this spectre:

(Sinister Spectre (CR 7): The dwarven spectre (Pathfinder RPG Bestiary 256) named Begrundi Stonehold seethes with anger. Originally part of a group of adventurers, this unfortunate soul was betrayed by his companions and left to die in the mountains. Dead for only a day before he rose as a spectre, Begrundi was able to track down his murderous companions before they could leave the valley. As the traitors slept in their camp, Begrundi killed them one by one, draining them slowly of their life force and delighting in their terror. Begrundi still roams the valley, preying on lone travelers. Since spectres abhor sunlight, this result happens only after sundown.)

I said that it only get the normal protection of the +2 deflection bonus and the +2 to the saves vs the Spectre (or a ghost). Am correct, or would it be treated as a summoned creature, and can't attack??

[Zaq]

If it wasn't summoned and doesn't have the Outsider keyword, it's pretty clear that neither of those things apply.

That said, if the character in question is trained in the relevant knowledge skill, you could consider allowing them to roll that knowledge skill to know that the creature wouldn't fall into the categories described in the spell. A successful roll could indicate that the character would know better than to assume that the spectre would be considered a summoned creature and therefore might be able to justify having not cast that spell; a failed roll could indicate that the character simply didn't know (or thought they knew but had incorrect information) and would need to just deal with the decision they made.

[Calthropstu]

If it wasn't summoned and doesn't have the Outsider keyword, it's pretty clear that neither of those things apply.

That said, if the character in question is trained in the relevant knowledge skill, you could consider allowing them to roll that knowledge skill to know that the creature wouldn't fall into the categories described in the spell. A successful roll could indicate that the character would know better than to assume that the spectre would be considered a summoned creature and therefore might be able to justify having not cast that spell; a failed roll could indicate that the character simply didn't know (or thought they knew but had incorrect information) and would need to just deal with the decision they made.

Confirmed. But the appropriate knowledge is knowledge religion, not knowledge planes. If he insists on knowledge planes the result should be "you know of no outsider that fits this monster. It attacks and hits through your spell. You can reasonably assume it is not summoned."

[Geddy2112]

Correct, the creature was not summoned, only summoned creatures are blocked from such contact. These creatures have to be summoned by a specific summon effect.

It would also protect against any kind of possession/domination the ghost could exert.