Psion said:
Are you not seeing any obvious solutions here? I am.
First - what is the PC's authority here? It appears enough that they can round up suspects with impunity. Answer: don't give them that sort of authority. Control the social situation. Perhaps the suspects are powerful nobles that the guard only has limited authority to do anything with without proof. Even if they find a suspect, the suspect may still be free to act, and unless they find what the suspect is up to (which may take more than surface thoughts), the players may still have a problem to grapple with.
Second - control the social situation. Add additional restrictions to make it harder. For example, make it so the PCs have to discover what is up without exposing their presence as investigators, or causing the suspect to bolt.
What's to prevent casting another detect thoughts? Well, if you have a sorcerer or telepath, perhaps nothing. But if you keep in mind the social situation, that could control it. People don't take well to spells being cast on them. In a society that is conscious of this, casting a spell in the middle of a chamber full of supposed suspects would be like waving a gun around at a polite dinner party. So, if you really want it to be subtle, you need silent and still spell (or hide power), which raises the level of the spell a bit. Even if PCs do have the resources, perhaps the enemy has resource to detect when a spell is in operation.
I agree.
How exactly are the PCs going to go out and restrain multiple suspects which may or may not have done anything and try to mentally interrogate them? Even under the most primitive legal system that can be considered kidnapping unless they have the sanction of the authorities in the area. Even with legal sanction you have to catch and restrain every one of them and hope your Detect Thoughts works.
First, if I remember correctly, detect thoughts takes several rounds of concentration on a 60' cone so it is pretty obvious when someone is trying it. Secondly, if I remember correctly the spell only catches surface thoughts. That means the person being scanned can control what the spell picks up if he knows that he is being scanned simply by thinking about something else. That is not the easiest thing to do but it can be done.
Speaking as a DM, most of the time when DMs complain about divinations, I have found out the real problem is DMs who don't fully read the description of the spell and/or give more information than the PCs are entitled to or DMs who for some reason assume that bad guys in the setting won't take divinaitons into account.
The primary rule of dealing with divinations is the 4-Corners Rule: do not give the PCs any more than what the text of the spell entitles them to. Almost all divinations are fairly limited when you look at them closely.
Detect Thoughts: Takes minimum 3 rounds of concentration at a target in a 60' cone just to learn what the target is currently thinking about, which for a character familiar with the spell, is what they want you to learn. It gives a save before the first round of information is in so you may not be able to gain anything from someone with a high will save. You also have to concentrate, and the target area is quite small so it is pretty obvious if you are doing it. The effect is also blocked by most solid materials so you generally have to have a clear line of effect or be doing it through some very thin walls.
Augury: Slow casting Time. Very small window (only 1 hour). Very limited answers Weal/Woe/Weal and Woe/Nothing. 9 in 10 chance at best of receiving an answer (unfortunately that remaining 1 in 10 also reads as Nothing). Note lastly that the spell only tells you if AN ACTION will bring good or bad results FOR YOU.
Divination: Even slower casting time. Same 1 in 10 failure but at least the caster knows it failed unless other magic is causing false results. This makes it clear that some magic does block divination. The spell also only gives an answer to a question about a SPECIFIC GOAL, EVENT, OR ACTIVITY THAT IS TO OCCUR WITHIN ONE WEEK. Do not bend on this. The spell does not answer questions directly about a person, only what he will do. Note also "specific" is subject to your interpretation as is "is to occur". The spell does not reveal information that happened in the past, not does it reveal something that MIGHT occur. It reveals an SPECIFIC something that IS TO OCCUR and no more. The spell is actually very lousy for investigating crimes (as my PCs found out) because it cannot tell you anything about the past.
Commune: This is one of the most powerful of divinations but it has serous drawbacks. The caster must ask questions that can be answered with a simple yes/no (but the deity can choose to give a short answer if it wishes to.) Note that the power you contact answers according to its agenda not the caster's. It also answers only to the limits of its knowledge (which can be limited indeed). Check Deities and Demigods for clarification on what a deity can see (check remote sensing). Very few deities can see into the past or future and even those can only do so under limited circumstances and for very small windows of time. This makes the spell nearly useless for investigating something.
Contact other Plane: Like commune but even more limited. You get fewer questions and the being contacted is not an ally so it has an even more limited list of possible answers. To top it off, there is a fairly good chance that the power doesn't know or simply lies and there is no real way of knowing. Of course, there is always the chance of stat damage from trying the spell, but that is actually fairly trivial to deal with.
Discern Location: Very powerful spell but with significant limitations. Little short of Mind Blank blocks the spell, but to find a creature you must have seen it (this implies that you must have seen what it actually looks like otherwise you haven't seen it you've seen its disguise), or have some item that belongs to it (not just something it touched or something random that it had in its possession). Finding an object is even harder because you must have touched it.
Scrying: This spell (thankfully) is much diminished in usefulness in 3.5. It is VERY slow casting and gives a save. To top it off, if the save is successful, you can't try again for 24 hours. It is also easy to detect (Int check) when it works and it has no audio at all. Visibility is only as good as your own eyes and the conditions at the scry location allow and it is very hard to scry someone you know little about (and you can't scry objects or places at all). Lastly you can escape the sensor by moving further than it can follow. Greater Scrying at least is faster but it has almost all of the other flaws.
Clairvoyance/Clairaudience: Location only. Slow casting. Limited range. Sensor doesn't move. Location must be known to you or at least it must be obvious that such location exists. Supernatural senses do not translate through the spell so it is subject to the conditions on the other side (except that it will allow you to see a bit if it is naturally dark.)
Tzarevitch