Saturday 4 July 2020

Circular Argument

Magic resistance in AD&D is not very precisely defined, although it’s not too bad compared to some rules. It is initially covered in the Monster Manual thusly:
Magic resistance indicates the chance of any spell absolutely failing in the monster’s presence. [Discussion of chance based on caster level and saving throws]. Note also that the magic resistance of a creature has an effect on certain existing spells such as hold portal, where it indicates the probability of the magic resistance shattering the existing spell.
By Monster Manual II the text had altered slightly:
MAGIC RESISTANCE is the chance a spell might fail when cast on the monster; this chance is expressed in a percentage.[Discussion of chance based on caster level and saving throws].
A creature’s magic resistance extends only to its immediate possessions, i.e., anything carried or worn. Area-effect spells will still function if targeted on a magic-resistant creature within their area. The creature itself might not be affected, although all others in the spell area will be subject to spell effects. A fireball, for example, may wipe out a cluster of orcs, while an agathion standing in their midst might be totally unaffected. The percent of magic resistance of a creature has an effect on certain existing spells such as hold portal, where it indicates the probability of shattering the existing spell.
This leaves the question of spell-like powers to the DM but I have never met or heard of a DM who actually ran a game where magic resistance did not affect these in the same way as it did spells. The question of what level the spell-like powers were cast at was generally settled either by the monster description or by the various hints here and there that HD should be used as a surrogate for level.
So, what about paladins’ protection from evil power?

Well, what about it? Surely it’s just another spell-like power and presumably it’s regarded as being of a level equal to the paladin?

Yeah. Just like those protective circles any character can draw with a bit of chalk…er, what?

The sixth level clerical spell ’aerial servant’ introduces the idea of the magical protection circle and the DMG presents these three as options for protection from the servant:

These are presented as an alternative to casting protection from evil and no spell is apparently required. Which fits with real-world folklore. Certain symbols simply keep certain monsters out.
Similarly, we are informed by the Monster Manual that demons can be kept out by a thaumatergic circle if lesser than a type VI, and ’special pentagram’ if they are that degree or higher.

Devils are a little less clear, but magic circles are effective, but have to be ’ensymboled’ in the case of greater or arch devils.

MMII tells us that a pentagram will keep out dæmons.

Up to this point, the power of these circles has been presented as a simple “if you are facing these, then use this” proposition. There is no hint that their use involves spell casting and basically, there’s no reason to think that they don’t work as advertised.

This introduces some balance questions as regards the power of demons and devils. Any street artist could render him/herself safe from the powers of Asmodeus using a bit of chalk and an umbrella, assuming they had a flat bit of space to draw and stand on.

My interpretation of how they work has always been that they are not “magic” in the normal sense, they are somehow expressions of the fantasy equivalent of physics. Gravity causes demons and devils to fall; magic symbols can cause them to be repelled. Maybe it’s a sort of phobia or a twisting of the planer effects that allows them to manifest in a different world.

Unearth Arcana then brings in the sixth-level magic-user spell ensnarement. This details the use of magical inscriptions of this type as prisons rather than guards. The spell itself is unusual in that the saving throw is actually an Int test between the monster and the magic-user who is trying to trick the subject into stepping through a gate-like portal.

For example, if the monster being summoned is a Type IV demon with an Int of 12, and the summoner has Int 14, the monster rolls 3d6, adds 2 for the difference in intelligence and if the result is greater than 12, the demon steps through the special gateway and finds itself in the diagram prepared for it, probably a pentacle.

There is some doubt but it seems that magic resistance is not applicable as the question is whether the demon falls for the trick and thereby steps through voluntarily.

But what about the portal - what about the gate spell in general? Magic resistance “indicates the chance of any spell absolutely failing in the monster’s presence”. In this case there would be at least a 60% chance of failure if we assume that the gate-like opening appears “in the monster’s presence”.
This is where I think the slight change to the description of magic resistance in MMII comes it. Now the effect “is the chance a spell might fail when cast on the monster”. Gate and ensnarement are not cast directly at the monster and both spells become much more workable when used on the sort of beings they are intended for, which generally have high magic resistance scores.

Once the monster is in the trap, a check is made to see if the diagram is correct. This is significant as the question appears to be independent of the spell and applicable to those trying to use the diagrams as protective mechanisms.

On usage, there is a chance that the diagram fails. Firstly, there is a base chance which can be brought to zero (and no further) by expenditure.

Always be careful
where you bleed
In classic AD&D style, the logic for this is somewhat dubious. A hand-drawn diagram has a base 20% chance of failure when used. This can be reduced by 1% for each 1000gp spent in combination with an extra turn’s work on the drawing. So it takes 20,000gp to reduce this to a base zero chance of failure.

Alternatively, the magic-user may have a permanent diagram inlaid or carved somewhere. This has a base chance of failure of only 10% but taking that down to zero is extraordinarily expensive: 50,000gp and an entire month of additional work (no guide is given about the base time needed).
When some creature is snared, there is a roll to see if the diagram works (assuming it’s the right type of diagram, of course). The failure chance is equal to the monster’s Intelligence score plus its HD (or level), minus the same score for the caster, plus the final base chance.

So, the Type IV demon has an escape chance of 23% (12 Int plus 11 HD). The caster is, let us assume, 12th level and adding this to their Int score of 14 gives 26, for a score of -3. The cheapest of inlaid floors would give the demon just a 7% chance of escape, a quick chalk diagram 17%. Higher quality materials and time could easily reduce this to no chance at all.

There is an issue here with the description of how circles work. The text says that inlaid circles need only be tested on first use. But there’s no guarantee that the second occupant of the circle is not more powerful and/or intelligent than the first. It seems unreasonable that a magic-user could summon an imp to “test” a circle before using it on Asmodeus. Not having any flaw that an imp can find is not the same as being able to hide shoddy workmanship from the gaze of the Master of Hell.

So I would suggest that each test establishes that the circle is proof against the intelligence plus HD of whatever has been captured. Ensnaring a second imp will work automatically; further rolling is needed for a more powerful target which, if successfully caught, then establishes a new “high score” of what can be held within the inlaid pattern.

Be that as it may, the question of magic resistance remains well and truly out of the picture.

So, where does this fit with the spell protection from evil?

The drawing of a circle as part of the spell seems only to be indicative of the range of the protection - 3’ diameter in the case of the basic spell, and 20’ in the case of the area effect spell.

Nothing more is needed than to draw a circle on the ground, or even in the air using the material component. As such, this is mainly a somatic component not directly connected with any of these diagrams, not even the lesser magic (protection) circle. So there is no real reason to view the repulsion field, once established, like other spell and subject to magic resistance.

As an aside, it’s worth remembering that magic-users are significantly more adept at this spell than clerics, not only do they cast the spells much more quickly (1 and 3 segments casting time versus 4 and 7), but magic-users get the 10’ radius spell as a 3rd level spell rather than the cleric’s 4th level - 32,500xp earlier.

To finally bring this back to our paladin, I can’t see any reason to treat their protection from evil effect any differently from the spell as regards the magic resistance roll.

This has an unpleasant effect for the paladin since all demons and devils have magic resistance.

The Paladin’s Problems

The objection has been raised by Skalding on that
Paladins are meant to be exceptional figures, holy exemplars of LG conduct. So holy that they are immune to disease, can cure by touch, and can sense the presence of concealed evil. One of their special powers is a constant circle of protection.
It makes very little sense to suggest that the circle hedges out summoned beings except for demons and devils because [insert one reading among many of a particular mechanic.] Even though demons and devils can be kept away by properly chalked circles, and devils repelled by holy objects
I sympathise with the reasoning but I feel that it misses out on some advantages of the paladin’s power. Firstly it is mobile, which a chalked circle is not, secondly it is 1" radius, not 10’. But more importantly it is constantly renewed.

It is hard to read the description of magic resistance’s effect on hold portal and not feel that it should have the same effect on a normal protection from evil spell, i.e., that it should dispel it if the resistance succeeds. At the very least it should allow the monster to encroach on its target for duration of the round.

Against the paladin that doesn’t work as the effect is a continual one without any need for concentration or casting. Breaching it once means nothing more than it has been breached once.

My xp calculations place the Type I demon at level 7. With a 50% MR, against a 7th level paladin the Vrok’s effective MR is a whopping 70%.

Pausing only to note that against any other class the Type~I has a 100% chance to be able to affect the character with its powers, let’s look at what this means in practise.

Against AC -1 the demon normally needs to roll 14, so it has a 35% of striking. Add in the effect of the protection and this drops to 24½%. So the paladin effectively has +2 to their armour against each attack.

And at the start of each round of combat there is a 30% chance that the demon will be forced out of melee range (offering a free attack at it’s back, I think) and have to close to combat again, which takes a round of combat where the paladin can be doing something else (I’m assuming that the demon already used its charge option for the turn, which of course had a 30% chance of failing).

If the demon chooses to attack from range then there is no question of magic resistance affecting the protection and the normal protection from evil modifiers of +2 to AC and -2 to saving throw targets apply. Which is weaker than what has been put forward for the drawn diagrams but of course it retains the advantage of mobility.

So I think the paladin is doing all right against an equally levelled monster and, again, it’s worth remembering that none of these partial protections are available to any other class, not even clerics.
So that’s sorted, then: static diagrams are powerful but limited, mobile spells and powers are more flexible but more vulnerable to MR. Job done.


The considerate summoner
always has a host body
(Art: Carlyn Hill)
We Need to Talk About Demogorgon

The Big D has a magic resistance of 95%, the highest in the Monster Manual and ignoring the odd MR mechanic of the daemons, exceeded only by the Crimson Death in MMII.

A protection from evil spell by an 11th level caster (or 11th level paladin) thus has only a 5% chance to have any effect on Demogorgon, and a 15% chance to keep Orcus at bay.

That seems fine to me. These are ultra-high level god-like monsters.

The problem comes with the magic item, scroll of protection from demons. What is its effect on Demogorgon?

If it is treated as a normal spell effect then Demogorgon’s magic resistance should penetrate it. We’re not given any guidance as to what level protections scrolls are but even if we assume an arch-mage has created the scroll, there is a 60% chance of the protection failing. And in fact there’s a substantial chance of it failing against any but the very weakest of demons - 15% against a Type I demon, for example.

This seems wrong for an item specifically stated as protecting against demon princes; it should do what it says on the tin.

One thought was that the scroll might actually create one of the diagrams perfectly. That fails on two points: firstly, a simple pentacle protects against all demons so there’s no reason for the progressive levels of protection for different powers of demons, and secondly the fact that the effect of the scroll moves with the user.

At this point I think we have to simply give up on trying to fit the protection scrolls into the magic resistance framework - they just don’t fit.

For my personal rationalisation of this I’m falling back on my old idea that there are things that can be done to the “space-time” of the PMP which can create spaces or barriers that the nature of certain foreign beings can not tolerate. In the case of the scrolls of protection from demons, protection from devils, and so forth the barrier prevents voluntary entry, but the monster can be forced in by the actions of the scroll user.

This twist in space may be created by magic but the result is not magical, in the same way that a dig spell creates a real hole (probably). As such magic resistance does not protect against the barrier.

What happens to a demon which is forced into the circle by an outside agent? That’s a DM call but I’d send them back to the abyss or wherever. But it would be like trying to get a cat into a bath, not something the creature would do willingly (presumably it’s extremely painful).

At the Table

The six types of protective circle below can be drawn by any character using various materials which may be available either at home or on an adventure. They can be used in various ways to attempt to protect a character or characters from some enemy, or to block portals. They are perhaps most useful for hiding from any detection powers or ESP employed by the relevant monsters.

In each case the base chance of failure, due to inaccurate measurements and other issues, is 20% (I assume that inscribing is not likely to be available as an option other than at home base). When the diagram is tested this chance is increased as usual by the INT and HD/level of whatever is attempting to breach the protection. Whichever character drew the diagram may subtract their own ability score from this. Furthermore, the various classes allow the artist to subtract their level or some proportion of their level from the failure chance, depending on the diagram and class:

Class Devices Mod
Magic-user All Level
Cleric All Level
Illusionist Magic Circle, Thuamaturgic Triangle Level
Druid Pentagram, Thuamaturgic Circle Level
Thief Pentgram Level-9
Paladin Pentagram, Basic Circle Level-8
Bard All Bard Level÷2
Monk Pentagram Level÷2
Thieves and paladins below 9th or 8th level respectively do not receive any modifier when their diagrams are tested for failure. Bards and monks round all fractions down.

In each case, “pentagram” includes the ability to produce a pentangle.

Finally, the DM may feel that an additional penalty is needed to reflect less than ideal circumstances, from 1% up to maybe 25%.

The Diagrams

Brief discussions of the devices follow, in each case the normal time to draw it is included in parenthesis.

None of this is quite by-the-book as there are inconsistencies and gaps in the book text. I’ve italicised particularly non-conformist parts of my own devising.

When referring to beings “from” a plane I generally mean native to that plane, so devils are from Hell, even though they may pass through to various other lower planes at will. The exceptions to this are the astral and ethereal planes. In those cases the diagrams block activity for any being currently on the named plane.

The Pentangle (5 rounds)

A pentangle may be placed on a location or object while a being not of the plane is magically held by other means within. If all exits from the prison are adorned with a pentangle, the magic effectively becomes permanent. The trapped being may not use any power or physical action in order to leave; at least one pentangle must be broken by some outside agency.

A pentangle can also be used to seal a reversed divination spell. For example, if  obscure object is cast on a magical sword and the sword placed into a case, if the case is sealed with a pentangle upon the lock(s) or bindings, then the spell effectively becomes permanent until the seal is broken. The object itself is contained by the seal and no special power or effect may be activated or utilised while it is so cloistered. Only one such item (or being) may be protected by any one case, room, or other container.


The Pentagram (6 rounds)

A pentagram will block the passage or attack of any creature native to planes 17 to 21 inclusive (see PHB p121). It will not block devils or arcanodaemons.

If a location, such as a room, has pentacles placed such that the outer circle touches each door-frame post, they will prevent entry by the above beings, even using teleport-no-error or such like. Similarly, sendings, detection, and all other powers will be unable to penetrate the location. Pentagrams so placed will not prevent the exit of such creatures or the effects of their powers from the room.
Protection Circle

The Basic Protection Circle (1 round)

This will block any lesser devil, and any hostile detection, sending, or similar divination power etc which is used by them or any caster of less than 6th level.

They may be used as described for pentacles for securing areas.


Thaumatergic Triangle

The Thaumatergic Triangle (5 rounds)

Tricky and thus slow to draw due to the uneven angles, this device prevents passage, sendings, powers etc. from beings originating in planes which are neutral - Concordant Opposition (if in use), and the Inner Planes, including the Ether, and also including alternate Prime Material Planes to the one occupied by the diagram, as well as creatures from planes 11 to 13, 15 to 17, 19 to 21, and 23 to 25.

May be used to prevent ingress as above except for beings on the astral plane of existence.

Magic Circle

The Magic Circle (2 Turns)

Blocks beings from planes 10 to 15, as well as 22 to 25, and the Astral plane.

May be used to prevent ingress as above except for beings on the ethereal plane.

Thuamaturgic Circle (2 Turns)

Blocks actions in the same way as the Thuamaturgic Triangle but is also effective against demons with less than 80% magic resistance (used here as a measure of power, not in the normal way).


Ingress blocking

The above assumes that the doors being protected are the only way into the location. If there’s a window, then that must be protected in some way too. The DM might want to allow pentagrams to be used in some way, or s/he may decide that more stringent requirements be met such as inlaying the gaps between bricks/stones/planks with lead or similar.

The object is to give a party in trouble some way to gain some breathing space. Since non-planer aid can usually be obtained by such beings which will be unaffected by diagrams, the rules above shouldn’t be too unbalancing.

What is “Extra-Planar”?

Travellers on other planes will find that a diagram meant to protect them from beings from that plane will have no more effect than a chalk circle will have on a mugger in the players’ home town.

Conversely, the players may find diagrams deployed against them as the “planer interloper”, as the DM sees fit or appropriate.

Moral Issues

While it is probably not an issue for Evil or neutral characters to use any of these diagrams, it may cause questions to be asked if a Magic Circle is used against creatures from the Upper Planes (Arcadia round to Gladsheim) by a Good-aligned character.

Gods and Wishes

Diagrams need to be limited in their power to some degree. They are vulnerable to damage by agents or other actors from the plane on which they exist as they have no effect on such beings and, for example, the cleaner might wipe away “those funny chalk marks” on the laboratory floor. But, still, it seems unreasonable that a deity would be adversely affected by them.

A wish should probably be able to destroy a diagram which the wisher can see.

Lesser deities should also probably be able to ignore diagrams they are aware of if the diagram was created by a demi-god or mortal. Greater gods should be able to ignore those created by lesser gods, demigods, or mortals.

This area is difficult as there are different conceptions of how gods should work in a gameworld; the DM must ultimately decide for themselves. Personally, however, I think that the ability to hide items using pentangles should be 100% proof against anything except very specific wishes by beings who already have a good idea where the item is hidden.