Being a good secret keeper: protection against mind manipulation

Question

In the D&D 3.5 universe, there are lots of spells and magical effects that read your mind, read and modify your memory, or otherwise force you to unveil the secrets you've heard.

I'm looking for the most complete list of non-removable sources of immunity to such things, most likely PrC class abilities.

I guess the Occult Slayer PrC's immunity to mind-affecting effects is a good start but

1. I don't know if it's enough;
2. I want the character to be friendly to everyone.

EDIT: my aim is to keep other people's secrets safe. Like "you can tell me, sure, it's not gonna leak from me". When I talk about secrets I've heard, it's not an idiom. I partially care about things I did ("I can come with you for that messon, nothing's gonna leak from me" - but some "who killed the guards?" divination might still work).

Answer 1

Occult Slayer is great for this

The Occult Slayer’s Blank Thoughts class feature does sound ideal for your purposes: it’s preventing anyone from prying secrets directly from your brain, and it’s Extraordinary, so no one can shut it down or suppress it. Quite possibly one of the “hardest” forms of protection in the game.

If your mind is your fortress, make sure you can stuff as much in there as possible: Autohypnosis

I strongly recommend training Autohypnosis, if you can. That way you can memorize even very long texts, avoiding the need to keep a hard copy that could get stolen.

Broader Protection: Mind Blank

The spell mind blank is almost-perfect immunity to snooping, seeing as it covers all [Mind-Affecting] effects and Divination effects that try to learn about you, explicitly covering “all devices and spells that detect, influence, or read emotions or thoughts.” With mind blank up, you literally need worry only about things that say they work despite mind blank specifically; if it doesn’t mention mind blank by name, it won’t work. Even the know secrets salient divine ability doesn’t break it.

Mind blank’s only real vulnerabilities are dispel magic and antimagic field/Dead Magic Zones. If someone takes down your mind blank, particularly if you only prepared one for the day thanks to its 24-hour duration, you might be in trouble. Boosting your caster level is always good, as are things like a Ring of Counterspells keyed to greater dispel magic. Master Abjurer (Master Specialist option, Complete Mage) gets a hefty bonus to preventing their buffs from being dispelled, for example.

If you can get mind blank as a Supernatural Ability, it becomes immune to dispelling and you therefore only need worry about antimagic field or dead magic zones. The Dweormerkeeper¹ prestige class from the Complete Divine web enhancement can turn any spell into a Supernatural Ability, for example; there may be other ways to get Su mind blank as well.

If you somehow get mind blank as an Extraordinary Ability or Salient Divine Ability, then it even works in an antimagic field. I doubt either is possible though. The Occult Slayer’s Blank Thoughts is better in these situations.

Vulnerability You Can’t Do Much About: Gods of Secrets

Between the two of these, all you need worry about are running afoul of deities’ portfolios. These can’t give the deity direct access to your thoughts, but they might discover things you’ve done, objects you’re hiding, and so on: any time something leaves your head and becomes a part of the external world, there’s probably a related deity who knows about it. Remember that there are gods of secrets out there; literally the act of keeping a secret itself informs the god about it.

Footnote

¹ Dweormerkeeper is easily in the top-10 most-powerful prestige classes in the game, and probably should be banned at the overwhelming majority of tables (in addition to being impossible to dispel, Supernatural Abilities also have no components – an Su wish, for example, does not cost XP).

Answer 2

Keeping secrets by gaining immunity to mind-affecting effects is relatively easy. The aforementioned mind blank spell is way high on the list, but so is just playing a creature who's naturally immune to mind-affecting effects. The adu'ja from Dragon #317 is a LA +2, no-racial-HD plant; the feytouched from the Fiend Folio is a LA +1, no-racial-HD fey with the extraordinary ability immune to mind-affecting effects; and Libris Mortis has a pay-the-money-and-XP-to-get-it necropolitan template to become undead.

Combine this with the feat Live My Nightmare (UA 94) to deter divination spells for added protection.

The following are not forever, and they're spells, so they might be of limited utility to you.

The programmed trigger option of the 9th-level Sor/Wiz spell programmed amnesia (SC 162-3) could be activated by a mental probe and then rewrite your brain; the spell's permanent (although not instantaneous).

The 4th-level initiate of Vecna spell Vecna's courier (Dragon #342 56) shoves a secret message that the shovee doesn't remember but the shover does into the shovee's brain; mundane means won't get that out of you--a password is needed. It lasts 1 day per caster level.

The 2nd-level Pal spell loyal vassal (SC 134) turns a mind-affecting effects' standard orders into suicidal orders, which often triggers another saving throw, but only if the order is "an attempt to make a loyal vassal" "harm [the caster] or anyone else affected by this spell"--so a liberal definition of harm is needed. It lasts 10 minutes per level.

Top off everything with the 8th-level Sor/Wiz spell mind of the labyrinth (DM 70) and, if you're seriously hardcore, the 3rd-level cleric spell infallible servant (EoE 27) and things should be pretty safe in your noggin. Both last 1 hour per caster level.

By the way, a particular campaign might allow swashbucklers to seduce to learn secrets as a function of the Bluff skill. Therefore one should remain hostile and unattracted to those who swing from chandeliers. Be especially wary of the Brd7/Swb4 who can succeed on the DC 70 Bluff checks to extract unutterable secrets from hostile characters.

Addition: Dragon #340 presents on page 55 moon-warded ranger substitution levels. The 11th-level moon-warded ranger substitution level grants the indomitable mind class feature, a supernatural ability granting immunity to "mind-affecting spells and abilities" except harmless ones (calling out bless and heroism specifically), which is a tough and interesting trade-off (not an extraordinary effect like the occult slayer's but still being able to get morale effects). It means taking ranger all the way to 11, but it also means not having to take occult slayer.