Is a subject aware of an enchantment if he fails a will save

Question

There are some spells (probably mainly enchantments) out there you have to make will saves and I am not sure if the subject is aware of the will save.

Let me give you two examples:

1. Someone scries on a subject. The subject has a Will save but if he fails does he know he has been scried?
2. Someone casts Aversion on a suject causing her to avoid an object or location. Is this person aware of it? Is the new behaviour suspicious to him?

Answer 1

As it says in the section on Saving Throws.

A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack. Likewise, if a creature’s saving throw succeeds against a targeted spell, you sense that the spell has failed.

It's also important to note that in Pathfinder, all spells, even those with no verbal or somatic components, have visible magical manifestations, and so can be identified by sight as they are cast.

So, if the target succeeds at the save, yes, they know something was attempted on them, and if they observed the caster casting the spell, then they are likely to put two and two together.

If the target FAILS the save, on the other hand, then it means the spell took full effect. Even if they saw the casting, they may not be aware they were the target, or that anything has changed. A target could make a Spellcraft check to identify the spell being cast (DC 15 + spell level), which might give them a clue. Or, if trained, they could make a Knowledge:Arcana check to identify the spell that targeted them, even if they couldn't see the casting.

Answer 2

The target has no special knowledge or lack thereof of such a spell's effects

While it may compromise such spells' usefulness, Aversion, Scrying, Dominate Person, Suggestion and other mind-altering spells (even Charm Monster) don't automatically conceal the fact they have been used from their subject. That said, subjects who fail their saves also fail to receive the automatic notification that a hostile effect has occurred.

For a spell like Aversion, this means that characters who are just wandering past the warded area are unlikely to notice its effect while characters specifically entering such an area would find the compulsion obvious.

For a spell like Charm Person it means that some creatures may attack you despite viewing you as a friend if they know you cast the spell on them, but would just have a really really good first impression if you cast it from hiding before approaching.

For a spell like Scrying there's no obvious sign of magic, so only creatures with detect magic or see invisibility or other such effects would have a chance to spot the invisible magical sensor and deduce the surveillance.

In general, enchantments need contextual preparation beyond just casting the spell in question if you want to heighten their believability so that the subject doesn't immediately suspect magical compulsion. And, of course, you should remember that subjects who succeed on their save are automatically notified that they were subject to a hostile magical effect requiring a Will saving throw.