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I personally would never say "Because I said so." However, I'm very likely to say "You don't know why, but something appears to be interfering with your ability to use magic."...telling people they can't play their character as they intended simply because you say so is weak-sauce.
"You can't do this."
"Why?"
"Because I said so."^ Is a pretty good indicator you need a smarter GM.
Exactly.
As a GM, you should have a reason. It should be a reason consistent with the rules of the world you created, but they players aren't entitled at all times to know exactly what that reason is or why things are the way they are.
Half the game is figuring that kind of stuff out.
For all the player knows they could be under any number of effects that either make them unable to cast spells or make them believe they are unable to cast spells.
A GM should be able to say "You don't know why, but something appears to be interfering with your ability to use magic." and have players accept it as part of the game in the same way they should be able to describe that a mountain is tall and have them accept that as part of the game.
I agree it is a problem if the GM doesn't justify it in the logic of the world, but the GM builds the logic of the world.
Look at the Mana Wastes, for example. The explanation is it is a wild magic area because of the wars between the magic users.
Why?
Because it creates a reason for one area to have firearms when other areas don't.
Why?
Because that was something they wanted to have in the world.
If the GM wants to have something that prevents prisoners from casting spells, and if the GM is consistent with how it works for and against players, there is no issue in that game. How they do it may not expand to other games, but it doesn't need to.
Stun, daze, blind,deaf, sleep etc. Many ways to go about it. There is the ye old grapple which shuts down so much stuff. Or as an earlier post suggested, throw a monk at them. They aren't as easy to handle, especially if the party is forcing saves. Something else would be ninjas with improved feint. How much sense motive do the casters have? Flat bab won't cut it. There is also the feat mageslayer. Bad news for casters and creatures with spell-lke abilities. The ony thing I wonder about with that feat is how the casters know they can't cast defensively. Almost as if the moment the character took the feat, they spend half their time announcing it to the world.
He's asking about how to keep them prisoners.
Unless you have a whole platoon of guys to take turns pounding on them. Those ideas won't work.
Oh. Damn. I think everything I can think of has already been suggested. Unfair.
Give the guards gas masks and fill the place with Stinking Cloud, problem solved.
I'm surprised no one has yet suggested this:
Robe of Powerlessness Pathfinder Core Rulebook, page 542
Aura: strong transmutation
CL: 13th
Slot: body
Weight: 1 lb
A robe of powerlessness appears to be a magic robe of another sort. As soon as a character dons this garment, she takes a -10 penalty to Strength, as well as to Intelligence, Wisdom, or Charisma, forgetting spells and magic knowledge accordingly. If the character is a spellcaster, the robe targets the character's primary spellcasting score, otherwise it targets Intelligence. The robe can be removed easily, but in order to restore mind and body, the character must receive a remove curse spell followed by heal.
CREATION -- Magic Items:
robe of the archmagi -- 37,500 gp
robe of blending -- 4,200 gp
robe of bones -- 1,200 gp
robe of eyes -- 60,000 gp
robe of scintillating colors -- 13,500 gp
robe of stars -- 29,000 gp
robe of useful items -- 3,500 gp
I think that "in order to restore mind . . ." can easily be interpreted to apply to spellcasting and thus require the two spells to regain.
At minimum it requires a 1,200 gp item to create and a 13th level caster. Even if the BBEG isn't one, or doesn't have one on staff, hiring a 13th level caster to cast a 7th level spell is CL X Spell level X 10 = 13 X 7 X 10 = 910; so I don't think its that unreasonable to have had the BBEG hire some NPC caster to have created it.
And its reusable, so you can hit all the casters you want. -10 STR is nice to slap on any prisoner (caster or not).
And its a robe, meaning cloth, meaning easily destroyed. Prisoners are draped in the robe until it takes effect and then removed from their sight. Once they gain their freedom, if some PC scours the dungeon for it because s/he wants it for the group's use, it is easy enough to say that other prisoners are escaping and some other escapee, in a fit of rage, has torn it to shreds, or burned it, whatever.
Roll up some "Spellbreaker" guards.
You can make some nasty anti-caster clerics if you put your mind to it.
You can completely specialize them in anti-caster stuff as they'd have normal guards for non-magic prisoners.
Give them some Merciful maces so they can beat the players into unconsciousness with zeal.
I find this is better than a simple "You just can't cast" option. The guards give the illusion that maybe a player can wait for a break and then use his spells to escape. It also allows them to use minor spells to assist in day to day survival.
A robe of powerlessness appears to be a magic robe of another sort. As soon as a character dons this garment, she takes a -10 penalty to Strength, as well as to Intelligence, Wisdom, or Charisma, forgetting spells and magic knowledge accordingly.
Because technically you don't lose spellcasting powers from taking a penalty to your casting score. So 'accordingly' it does nothing.
This is obviously not what was intended and it's a fault of not making sure all language was converted correctly when they changed how penalties, ability damage and ability drain works, but it is still there.
I'd think the obvious solution is to have one's uber-powerful DMPC rescue the PCs before the sorcerer player has a chance to try anything. that has two benefits:
1. It emphasizes just how much cooler the DMPC is compared to the PCs.
2. It forces the PCs to be grateful to the DMPC for rescuing them, giving the DM an escuse for having them tag along with the DMPC and see how great he is.
See? Simple!
By that logic, Abraham, touch of idiocy has no effect on spellcasting either.
The truth? It does. Why? Not because of the penalty (as you say, that has no effect on spellcasting), but because it says it has an effect on spellcasting. In short, the robe and touch of idiocy are exceptions to the rule.
I called it out as an error long ago, and as usual the developers swooped in and decided to cover their mistakes by claiming it was their intent all along.
By that logic, Abraham, touch of idiocy has no effect on spellcasting either.
The truth? It does. Why? Not because of the penalty (as you say, that has no effect on spellcasting), but because it says it has an effect on spellcasting. In short, the robe and touch of idiocy are exceptions to the rule.
I called it out as an error long ago, and as usual the developers swooped in and decided to cover their mistakes by claiming it was their intent all along.
Except the robes say they function accordingly -- I agree, it is obviously an error... but it's still there. "Accordingly" means according to normal rules... which means it doesn't do anything.
I would never expect this to fly at the table, but I do want to point it out so people are aware because out there is a player who will point this out and expect it to fly.
forewarned is forearmed (and if the forearm doesn't work use a club!).
A wizard gains bonus spells based on his Intelligence score. The minimum Intelligence score needed to cast a wizard spell is 10 + spell's level.
Clerics, druids, and rangers get bonus spells based on their Wisdom scores. The minimum Wisdom score needed to cast a cleric, druid, or ranger spell is 10 + spell's level.
Bards, paladins, and sorcerers gain a number of bonus spells based on their Charisma scores. The minimum Charisma score needed to cast a bard, paladin, or sorcerer spell is 10 + spell's level.
Assumptions:
(1) All gear, magical or otherwise has been removed from the prisoners, so there is nothing giving the spell caster a bonus to their spell casting ability score.(2) Spell caster has a 20 in their spell casting ability score.
(3) Spell caster has no inherent bonus raising the score above 20.
Conclusion:
(1) Having worn a robe of powerlessness, their spell casting ability score is reduced to 10.
(2) They'll be able to cast 0 level spells only. First level spells would require an 11 ability score.
If the spell casting ability score is less than 20, then they won't even be able to cast zero level spells.
Abraham spalding, would you please clarify how this constitutes doing nothing?
Do not...I repeat, DO NOT make a personal antimagic field generator. Remember, anything you create can and will end up in the PCs hands. Are you looking forward to a barbarian that's immune to magic. Sure he can't use magic items, but nothing short of dragons and adamantine will stop him (and sometimes not them either).
A wizard gains bonus spells based on his Intelligence score. The minimum Intelligence score needed to cast a wizard spell is 10 + spell's level.
Clerics, druids, and rangers get bonus spells based on their Wisdom scores. The minimum Wisdom score needed to cast a cleric, druid, or ranger spell is 10 + spell's level.
Bards, paladins, and sorcerers gain a number of bonus spells based on their Charisma scores. The minimum Charisma score needed to cast a bard, paladin, or sorcerer spell is 10 + spell's level.Assumptions:
(1) All gear, magical or otherwise has been removed from the prisoners, so there is nothing giving the spell caster a bonus to their spell casting ability score.
(2) Spell caster has a 20 in their spell casting ability score.
(3) Spell caster has no inherent bonus raising the score above 20.Conclusion:
(1) Having worn a robe of powerlessness, their spell casting ability score is reduced to 10.
(2) They'll be able to cast 0 level spells only. First level spells would require an 11 ability score.If the spell casting ability score is less than 20, then they won't even be able to cast zero level spells.
Abraham spalding, would you please clarify how this constitutes doing nothing?
Absolutely.
Conclusion 1 is flawed. You are assuming that a penalty reduces abilities scores -- it doesn't. Ability Drain does that, and a few other specific effects.
Ability penalty doesn't remove the ability to cast spells:
Some spells and abilities cause you to take an ability penalty for a limited amount of time. While in effect, these penalties function just like ability damage, but they cannot cause you to fall unconscious or die. In essence, penalties cannot decrease your ability score to less than 1.
For every 2 points of damage you take to a single ability, apply a –1 penalty to skills and statistics listed with the relevant ability. If the amount of ability damage you have taken equals or exceeds your ability score, you immediately fall unconscious until the damage is less than your ability score. The only exception to this is your Constitution score. If the damage to your Constitution is equal to or greater than your Constitution score, you die. Unless otherwise noted, damage to your ability scores is healed at the rate of 1 per day to each ability score that has been damaged. Ability damage can be healed through the use of spells, such as lesser restoration.
Intelligence: Damage to your Intelligence score causes you to take penalties on Intelligence-based skill checks. This penalty also applies to any spell DCs based on Intelligence. A character with an Intelligence score of 0 is comatose.
Wisdom: Damage to your Wisdom score causes you to take penalties on Wisdom-based skill checks and Will saving throws. This penalty also applies to any spell DCs based on Wisdom. A character with a Wisdom score of 0 is incapable of rational thought and is unconscious.
Charisma: Damage to your Charisma score causes you to take penalties on Charisma-based skill checks. This penalty also applies to any spell DCs based off Charisma and the DC to resist your channeled energy. A character with a Charisma score of 0 is not able to exert himself in any way and is unconscious.
Please note that ability penalty works much like ability damage and ability damage doesn't remove casting ability. Of the three things ability drain is the only thing that according to normal rules removes spell casting ability.
Now as Ravingdork correctly pointed out specific things like touch of idiocy specifically state they are a penalty and remove spell casting ability for the time as well, but they explicitly state both parts of this. Feeblemind on the other hand specifically changes the ability scores in question to 1... it isn't penalty, damage or drain it's a specific change to ability score.
Now if they wanted RAW to match RAI then they should have either made the robes give ability drain while worn or explicitly state that the penalty removes spell casting ability like touch of idiocy does.
Again it isn't my position that anyone should try to do this in game -- only that on the theorycraft and legalese side there was a screw up.
Finally I would point out that I didn't say it does nothing... I said it doesn't remove spell casting ability. These are not the same thing as the penalty still lowers the bonus for concentration checks, and the DC for spells cast.
AH! I see our difference. Where you're quoting from it talks about "a limited amount of time." The robe of powerlessness isn't limited in duration; it is permanent unless acted upon by remove curse and heal.
For me, that puts the robe's -10 penalty in the ability drain category and not the ability damage category.
I see it that way because ability damage heals of its own accord, but ability drain is permanent until a restoration repairs it.
Since the robe's penalty is permanent until restored and doesn't heal over time, I see it as a drain and not damage. Furthermore, the item description says it removes spell casting ability, which drain would do, but damage wouldn't.
True, the item description doesn't explicitly state the -10 penalty as damage or drain, so I admit that it is up to interpretation.
But the OP could use it as such without violating RAW, imo.
AH! I see our difference. Where you're quoting from it talks about "a limited amount of time." The robe of powerlessness isn't limited in duration; it is permanent unless acted upon by remove curse and heal.
For me, that puts the robe's -10 penalty in the ability drain category and not the ability damage category.
I see it that way because ability damage heals of its own accord, but ability drain is permanent until a restoration repairs it.
Since the robe's penalty is permanent until restored and doesn't heal over time, I see it as a drain and not damage. Furthermore, the item description says it removes spell casting ability, which drain would do, but damage wouldn't.
True, the item description doesn't explicitly state the -10 penalty as damage or drain, so I admit that it is up to interpretation.
But the OP could use it as such without violating RAW, imo.
Except it specifically states penalty -- which of course is a penalty. The item description doesn't say it removes spell casting ability, it states it does so 'accordingly' -- accordingly to what though? Since it doesn't say it goes to the normal rules for such things and those of course are what I quoted above.
A penalty to an ability is its own thing -- it doesn't 'convert' to damage or drain unless something else (or itself) specifically states it does.
For example the penalty to strength can't knock you unconscious since it's a penalty and those can't do that.
The time limit (or lack there of) has nothing to do with anything other than bonuses.
It doesn't need to beyond the fact that it proves that no matter how long it lasts it doesn't change from penalty to damage or drain -- which was my point -- and since it isn't drain and a penalty doesn't actually lower your ability score for the purpose of what spells you can cast it doesn't work as advertised by RAW.
Again I get it by RAI, and wouldn't try to push this angle in a game, but that doesn't mean it is written correctly or shouldn't be fixed.
According to what? According to the -10 penalty. If it states that it removes spell casting ability, which it does, then that -10 penalty is a drain and not damage. Because if it were damage, as you claim, it wouldn't remove spell casting ability, except, of course, that the item clearly states that it does.
But let's say it is damage and not drain. If 2 points of damage makes one apply a -1 penalty to skills and statistics, then a -1 penalty to skills and statistics causes 2 points of ability damage. A -10 penalty equates to 20 points of ability damage. Recall that the robe of powerlessness says a penalty, not damage.
This damage does not actually reduce an ability, but it does apply a penalty to the skills and statistics (emphasis added) that are based on that ability.
To what statistics based on that ability could the book be referring? It already specifically states skills are affected, so those aren't the statistics to which it is referring. Spells (as in, the number known and/or the number that can be cast per day) are a statistic that is based on the ability.
The section on p. 555 doesn't specifically state that spells are lost due to ability damage, but neither does it say that they are protected.
I see an item that says it causes a penalty to an ability (and doesn't specify that it is ability damage) and then says that spells and magical knowledge is forgotten. Since spells and magical knowledge would only be forgotten if the penalty to the ability was an ability drain, then it is an ability drain.
Some spells and abilities cause you to take an ability penalty for a limited amount of time. While in effect, these penalties function just like ability damage
Some. As in, not all. So, while these limited duration spells and/or abilities are in effect, they act like ability damage.
The robe of powerlessness affects abilities permanently unless a combination of remove curse and heal are cast, in the same way that stone to flesh is permanent unless a break enchantment or flesh to stone is cast on the victim. Therefore, the robe of powerlessness does not fall into the category of "for a limited amount of time."
Since some spells and abilities cause you to take an ability penalty for a limited amount of time, there must be some spells and abilities that operate differently. Differently as in for a permanent amount of time; which is an ability drain because they're restored only by a restoration.
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The Robe of Powerless tactic seems rather cheesy to me. Cursed items are supposed to be a kind of trap for careless PCs; that's why they generally don't allow saving throws. Cursed items are intended to hit the person who decides to use them, not someone they're forced on.
If you read the RoP strictly, it's got problems, too:
A robe of powerlessness appears to be a magic robe of another sort. As soon as a character dons this garment, she takes a –10 penalty to Strength, as well as to Intelligence, Wisdom, or Charisma, forgetting spells and magic knowledge accordingly. If the character is a spellcaster, the robe targets the character's primary spellcasting score, otherwise it targets Intelligence. The robe can be removed easily, but in order to restore mind and body, the character must receive a remove curse spell followed by heal.
If it's put on an unconscious character, did that character don the RoP? The way it's written, it has to be the character's action to don the robe.
Anyway, what does "targets the character's primary spellcasting score, otherwise Intelligence" mean, given that it also penalizes Str, Int, Wis, Cha? Was the writer hedging his bets in case someone ever writes a Con or Dex caster class?
Shot from the hip (and from plain imagination):
"Spell-Shackles"
A (arcane) caster bound with these heavy metal handcufs cannot cast spells with a somatic component and must make a concentration check against DC 25 + (2x Spell level) in order to cast a spell.
If he fails, he receives 1d6 non-lethal damage per spell level (or caster level!).
If he succeeds he receives TWICE that amount (or the same but lethal!).
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On the otherhand, simply gagging and tieing them up works as well...
Cut off his hands and remove his tongue.
.
.
Or you could just bind and gag him. Jail cells / manacles with anti-magic fields would also work.
Make them run out of hit points!
Put bleed effects on them (caster takes bleed damage on his turn, forcing a conc check)
Hold your action to their turn and swat them with a sap (or two if twf) making them take even *harder* conc checks! (added bonus, eventually they go unconscious...unconscious targets are the bestest targets!)
And the corellary to the above quote:
"Cut off the head, or destroy the brain"
WE'RE COMING TO GET YOU BARBARA!!!
Stuffs
Look Mykull if you want to hash this out feel free to dig through the archives for one of the multitude of threads where it's already been hashed out first. I really don't feel like going over old territory anymore.
Penalties don't cause the stats to actually be lowered just like damage doesn't. That's a property of ability drain.
Here's a starter for you:
Q: I am confused on the different types of Ability Damage, Drain, and Penalty. Plus some spells like ray of enfeeblement and touch of idiocy seem to even have special rules. How do these effects really work?A: (James Jacobs 4/23/10) Ability damage only results in a penalty to actions associated with that ability score; it does NOT make you lose access to feats or spells that require ability score minimums, since your actual ability score does not lower. Only ability DRAIN can make you lose access to spells you can cast or feats that have prerequisites. But it's not that simple. Some effects that cause ability damage or ability penalties DO have additional effects. Touch of idiocy is one such spell, since it says in the spell's description that it affects the target's ability to cast some or all of its spells if the penalty imparted to the ability score drops low enough. This is an exception to the general rule for ability scores and applies only to touch of idiocy (the point of the spell, really, is to be a lesser version of feeblemind that screws over spellcasters, after all). Ray of enfeeblement, on the other hand, does NOT have this type of language. It merely works as a normal penalty to an ability score.
Q: A 12th-level wizard with a 16 Intelligence takes a 3 point Intelligence penalty from Touch of Idiocy. What is the highest level spell he can cast, sixth or third?
A: Third.
Q: A 12th-level wizard with a 16 Intelligence takes 3 points of Intelligence damage. What is the highest level spell he can cast, sixth or third?
A: Sixth.
Q: A 12th-level wizard with a 16 Intelligence takes 3 points of Intelligence drain. What is the highest level spell he can cast, sixth or third?
A: Third.
Q: A fighter with 13 strength and the Power Attack feat takes a 3 point Strength penalty from Ray of Enfeeblement. Can he Power Attack?
A: Yes.
Q: A fighter with 13 strength and the Power Attack feat takes 3 points of Strength Damage. Can he Power Attack?
A: Yes.
Q: A fighter with 13 strength and the Power Attack feat takes 3 points of Strength Drain. Can he Power Attack?
A: No.
Now should the robes perform how they were intended too? Yes. Are they written correctly to do that? No.
Now for something completely different:
Have the casters marched down to the Spell Dump every morning. Pick a first level spell that has a visible effect (i.e. Summon Monster 1, Burning Hands) and force the caster to cast that spell over and over again, using up higher level slots to cast that spell. There are several guards to deal with the spell's effects. Include some pain to make sure all the spells are cast (that's part of a torturer's job). March them back to their cells.
And if a character wants to not cast all their spells?
DM Torturer: "Is that all your spells?"
PC: "Uh, yeah."
DM: Roll a Bluff check, it is opposed by the torturer's Sense Motive.
Aside: Torturer should be an Expert with Sense Motive as a class skill.
DM: He beat you. So, he beats you until you cough up the spell he knows you have.
Ascalaphus: The verb "don" does mean "to put on" and that implies certain action on behalf of the wearer. But one doesn't have to don armor all alone. If one has help getting into their full plate, one would still be said to have donned it. I believe earlier in the thread it was established that unconscious characters are considered willing. So I think an unconscious character could have a robe of powerlessness put on them and still work.
There's also:
GUARD: Option #1, we cut out your tongue and lop off your hands. And if the guards happen to notice any spell-like effect emanating from your area, we'll just kill you and call it self-defense. Option #2, you put this robe on.
PC: Hmmmm, I guess I'll take the robe.
And even getting the tongue and hands removed could be returned with a regenerate spell. It'll handle severed body parts, broken bones, and ruined organs. Yes, yes, yes, the tongue is a muscle, but I consider it a severed body part even though it isn't specifically listed.
To clarify, the robe penalizes Strength and one of the following: Intelligence, Wisdom, or Charisma (depending on which ability affects spell casting). If the wearer isn't a caster, then it is Intelligence.
But imprisoning characters not at first level is always a little cheesy.
Abraham spalding, I understand the difference between ability damage and ability drain. You say that the way the robe is written doesn't cause spells to be lost. I say that it does. I'll try a different explanation, with your quote:
Some effects that cause ability damage or ability penalties DO have additional effects.
. . . forgetting spells and magic knowledge accordingly.
Accordingly to what? In accordance with what James Jacobs wrote, "Some effects that cause ability damage or ability penalties DO have additional effects."
That isn't RAI, but RAW, because, well, its written in the item description. I haven't had this discussion before, so I'm game to go at it, but I understand you feel this has been hashed out elsewhere and won't be responding to it.
But accordingly it does nothing -- it doesn't say you lose spell casting ability, it says you lose spell casting ability according to the rules for penalties which doesn't cause a loss of spell casting ability. I mean really consider touch of idiocy where it explicitly states the loss, then consider bestow curse which does the exact same. Then this states, "Oh you get this penalty and then forget spells and magic knowledge accordingly." Accordingly to what? It doesn't say this sidesteps the normal rules, it doesn't say this penalty is like that of touch of idiocy or bestow curse it just says you forget accordingly, which is to say you don't. Heck the 'magic knowledge' could be as easily defined as, "The decrease in DC and concentration checks that you take for penalties" or simply the penalty on knowledge checks since there isn't 'magic knowledge' in the game beyond spellcraft and knowledge(arcana) -- it was written extremely poorly in context of what they did with the changes in penalties, damage and drain.
Accordingly nothing since accordingly in this case does nothing.
I didn't noticed there were still so many good suggestions in this thread, sorry my bad,i thought i read already everything there is to know about my question.
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Given everything I've seen in this thread so far, my favorite is to hold someone/something the PC cares about hostage, while giving the PC a lot of freedom to walk around. Just while wearing a collar that detects if they cast a spell and sends a kill-signal to the hostages.
It stops the character from escaping with magic, forcing the player to find a solution without magic. That's a significant challenge. But the player can still do things. For example:
- try to subvert the guards
- try to find out where the hostages are kept
- negotiate with their captor
- reach the rogue with enough Disable Device to remove the collar without setting it off
Whereas if you drug them out of their mind or perform some sort of (magical) lobotomy, the player can't do much more than go play video games or read comic books.
*about penalties*
Abraham is correct. Penalties do not hamper spellcasting. Nor do negative levels. Hell, even ability damage doesn't. A wizard can walk around with a 1 Intelligence due to penalty or damage and happily throw around time stop as often as he wants, and doesn't even lose his bonus spells or have skill point issues, lose the ability to speak, or anything like that.
A creature that drains spells could be used. I think an intellect devourer does something like that.
If it is high level, you could have a diviner figure out which spells they have and sit outside their cells taking a readied action to counter each one as it is cast.
it says you lose spell casting ability according to the rules for penalties which doesn't cause a loss of spell casting ability.
A robe of powerlessness appears to be a magic robe of another sort. As soon as a character dons this garment, she takes a -10 penalty to Strength, as well as to Intelligence, Wisdom, or Charisma, forgetting spells and magic knowledge accordingly.
It does not say what you say it says. Those words are not there.
Abraham, allow me to clarify one thing: I UNDERSTAND YOUR POINT! You keep making it like I don't comprehend the words you're typing on the screen.
You think that all ability penalties take the form of ability damage (which does not cause the loss of spells). And that the only exceptions, despite James Jacobs rather liberal, "Some effects that cause ability damage or ability penalties DO have additional effects," are those that very explicitly state that, like bestow curse or touch of idiocy. Furthermore, you think the robe is intended to work they way I describe it, but that it is not written that way.
Allow me to iterate: It is not that I do not "get it," it's that I don't agree with your interpretation of this specific item. I think it does what it is intended to do as written. Here's why:
(1) It is not a robe of less power, but a robe of powerlessness. As in, without power. The ability to cast spells is a power.
. . . spells are a source of immense power.
A robe of powerlessness should leave one without power (i.e. the ability to cast spells). You might say that's RAI, not RAW, except, powerlessness is written, right there, on page 542.
(2) Since it says right there in the item description "forgetting spells and magic knowledge," then you forget the spells and magic knowledge (knowledge (arcana), spellcraft, knowledge (religion) as it applies to divine magic, the purpose of spell components on your person, how to read the arcane script of your spell book, the magical applications of your divine focus) because that's what is written.
(3) ACCORDINGLY.
Twice you have asked the question, “According to what?” Twice I have answered it. Once, by saying that it is in accordance with James Jacobs' quote. Then, I assumed that the penalty is ability damage and not drain and pointed out that the number of spells one can cast is a statistic of that ability score and would thus be affected.
Here's a third response to your question:
Not all penalties are damage. A penalty to using improvised lock picks is not because my hands are damaged, or my masterwork picks are damaged, but because I'm using substandard equipment. My point here is: NOT ALL PENALTIES ARE DAMAGE. If true, then adjectives applied to those nouns would not change that truth and not all ability penalties are ability damage. If that is true, then some ability penalties are something else; as in an ability drain.
Sufficient ability drain to a spellcasting ability score causes the lose of spells.
The robe of powerlessness causes a loss of spells.
The robe of powerlessness causes a -10 penalty.
This -10 penalty is an ability drain.
The item doesn't specify the -10 as ability damage (or as ability drain, either), only that it is a penalty (which, hopefully, I've established at this point is not always damage). Since the item says it causes the loss of spells, then, in this item, that penalty is a drain.