Casting Spells

What actually happens when a AD&D™ magic user casts a spell?

According to the DMG1 p.40 and PHB2 p.81, the process started some time previously, when the mage spent 15 minutes (in AD&D2, 10 minutes) times the level of the spell "memorizing" it from their spell book. This normally requires that the mage have their spell books, peace and quiet, and be well rested. DMG1 p.40 gives a table of the amount of rest (normally sleep) required before this can be done, according to the level of the spell to be memorized. One some DM's planes, the mage may find that this needs to be uninterrupted and comfortable sleep (this can be very inconvenient on wilderness adventures, though a good way of  getting out of standing watches!). If the mage is of a race that does not sleep (liches are a common example), then some form of meditation is usually required instead. On some planes, even those mages that do need sleep may be able to memorize spells after a suitable lengthy period of meditation. This has the advantage that, while it is quite hard to sleep more than once a day, it is possible to meditate several times a day. For 1st or 2nd level spells, where only 4 hours rest are required, a Wizard might manage to sleep 4 hours, spend 2 hours memorizing his 4 first level spells, and then cast them, twice a day, giving eight first level spells a day (for example when desperately Mending his employer's charger's barding that his pet Rust Monster half-ate!). With periods of meditation, this could be increased to 12 or even 16 first level spells in a day, though few mages would be able to maintain this for long.

On some planes, the mage may find that nothing of any significance can be done between sleeping and memorizing spells (getting up, having breakfast, but no spell-casting or traveling). If this stricture does not apply, then there is no obvious reason why the mage cannot memorize a spell, pause briefly to cast it, and than rememorize it. The spell numbers given on PHB1 p.26 (PHB2 p.30) are maximum numbers of spells memorized at any one time. Unless the mage is on a plane where this is also the maximum number of spells that may be memorized during any one day, then this allows a mage to cast a great many spells per day, as long as they are low level spells and the mage need do nothing else. For example, even working only an 8 hour day, any mage could cast 32 Mending spells this way, or ten Dispel Magics.

For an 18th level mage, rememorizing their entire spell list takes nearly 35 hours (just over 23 in AD&D2). It is obviously ridiculous for a mage to expect to do this in one stint, even if they have had 12 hours sleep previously. I would advise mages not to exceed 8 hours spell memorization (32 spell levels in AD&D1, 48 in AD&D2) except in emergencies, as magical overwork in well known to cause nervous exhaustion.

On some planes it is possible to "demote" spells: instead of memorizing one of your allowed number of high level spells, you can memorize an extra spell of a lower level. This can be very handy if you have a lot of useful spells at one level, and few at some higher one. Of course there are some mages who will just memorize 13 Fireballs when they are 12th level, but then what do they do when they need to teleport away in a hurry? The loss of flexibility in having many copies of one spell is almost never worthwhile, unless you are certain of exactly what situation you are going to meet. It is usually better to have a wide range of options than to be able to do one thing many times. It should be born in mind that demoting a spell represents a reduction in total power: you are carrying less spell levels of spell around with you. On the other hand, when what you really need is a Rope Trick, any number of third or fourth level spells are not going to help. Spell demotion is a useful addition to the techniques of a careful and thoughtful mage, and it is always worth experimenting to see if it is possible on your home plane.

But what is actually happening when a mage "memorizes" a spell? Since the mage already had already learnt the spell (and it was already counting against their maximum number of spells per spell level for their INT), and indeed the mage can "memorize" multiple copies of the same spell, it is evident that "memorize" is not really the correct verb. "Store" or "charge up" would be better, as PHB2 p.81 makes clear. By using their spell book, the mage slowly summons magical energy ("mana") and shapes it into the spell, storing the result in their mind ready to be released rapidly in combat by a few words and gestures. Just what is involved in this process, apart from the spell-book, peace, quiet, and a well rested mage, is not explained. I would expect that it also involves a good deal of mental gymnastics, repetitively chanting the words, and probably some ritual equipment, incense etc. All of which tend to attract the attention of passing monsters! The stored magical energy of all the spells memorizable by a high level mage is appreciable, and on many planes this is sufficient to cause them to detect a faintly magical. This it is only faintly, compared with the way they would register if all the spells were cast, is because the flow of mana from a memorized spell is small (after all, they do not leak away,  even if it is months since they were memorized), while in a cast spell it is quite large, and is normally much increased by mana flows summoned from other planes.

It states in PHB2 p.81 that a mage cannot get rid of a memorized spell, in order to replace it with another one, without casting it. This seems a very unfair rule: while casting a spare Fireball to get rid of it is merely inconvenient (particularly in built up areas, or confined spaces underground), some spells require extremely expensive components to cast, or age the caster or even lose them points of constitution. If this rule is strictly applied on a plane, then local mages should take great care before memorizing such spells that they are really going to require them. The problem of the effects of the spell going off (such as unwanted Fireballs) are easily avoided: according to PHB2 p.85 if the spellcaster's concentration is disrupted during spellcasting, for example by being struck by a weapon or failing a saving throw, then the spell is wasted in a fizzle of useless energy. This effect can be easily and painlessly duplicated out of combat by starting to cast the first segment of a spell, and then pausing part-way through to eat some nuts and daydream about the innkeeper's daughter. The spell that you started will be wasted, without any loud or disruptive magical effects. More seriously, I would suggest that any referee allows a mage to deliberately dump a memorized spell, simply allowing the structured mana they have stored to leak away harmlessly, rather than casting it. Since, as discussed below, the mana stored by the mage is small compared with that which the cast spell will summon from other planes once cast, there should be no deleterious side effects to this, nor any use of expensive spell components.

When the spell is cast, the magical symbolism of the words of the verbal components, the gestures of the somatic components, and the magical influences of the material components reinforce the structure of the spell, trigger it to activity, and direct it to the particular target the mage is casting it at. (On most planes, the final decision of targeting is made in the last segment or so of the spell, allowing the Fireball to be shifted a little if the front rank have advanced during the intervening few segments. On others however, the targeting must be decided the beginning of the casting, which requires considerable care and forethought by the mage.) The spell then uses its stored mana to reach out to one or more other planes, and tap the potential difference between them, or between them and the Prime Material plane on which it is cast. The planes used are normally the Positive and/or Negative Material Planes, depending upon the spell. (For fire or heat spells, the Elemental Plane of Fire is used instead or as well; for wind or lightning spells, the Plane of Air; for water or acid spells, the Plane of Water; and for stone spells, the Plane of Earth. ) This mana flow involves much greater amounts of mana than those originally stored by the mage during memorization. (Psionics, on the other hand, does not appear to involve summoning mana from other planes. The huge amounts of mana that must be expended directly, and very rapidly, by a psionic creature explains why on most planes humans are incapable of psionics, and even on those planes where they can, the necessary talent is very rare. Psionics is normally confined to highly magical creatures such as Mind Flayers, Demons, or Lammasu.) This flow of mana from other planes continues for as long as the spell lasts, and this is what is detected by a Detect Magic spell.

It is evident from many separate sources (eg. spell memorization and (most) casting times) that the initial amount of stored mana required to cast a spell is directly proportional to its spell level, ie an eighth level spell requires twice as much mana as a fourth level spell. On the other hand, the amount that can be done with a spell seems to increase much more rapidly than that (compare similar spells of different levels, eg the various Bigby's Hand spells). After a good deal of consideration, we have come to the conclusion that the mana summoned from other planes by a spell once it has been cast roughly doubles for every two spell levels of the spell (1st: 1, 2nd: 11⁄2, 3rd: 2, 4th: 3, 5th: 4, 6th: 6, 7th: 8, 8th: 12, 9th: 16). Another factor that is important for a spell is the level of casting, ie the experience level of the caster who cast it (or equivalent if the spell came from an item). We belive that increasing this does not correspond to increasing the amount of mana (ie a Fly spell cast by a 25th level mage does not detect as being any more magical than on cast by a 5th level mage), but rather to the skill and accuracy with which the spell was constructed, and thus to the efficiency with which the mana is made to do work. (This provides a good rationale for the dice limits on variable damage spells  in AD&D2: you can't get more than 10D6 out of a 3rd level spell, even if you connect it directly to the hottest part of the Plane of Fire, and even getting 10D6 takes a good deal of skill.) Note that it is  perfectly possible for an item to cast a high level spell at a low level of effect, eg. a Wand of Force casting Wall of Force at 6th level, which suggests that the skills involved in casting a spell at a high level of effect, and those involved in being capable of memorizing it in the first place are different, though they are learned together by magic-users.

If the flow of mana is interrupted, either by the spell being covered by an area of Anti-Magic, in which the flow of mana from other planes is prevented, or by the brief glitch or pulse of mana of a Dispel Magic, then the spell collapses. If the spell is one from a permanent continuous magical item, such as a +1 Sword or a Ring of Invisibility, then the structure of the spell is built into the item, along with a sufficient store of mana to restart it, and it will start to function again after it has been dispelled/moved out of the Anti-Magic area. This normally takes 1 round (D4 rounds in AD&D2) for the spell to recover after the jolt of successful Dispel Magic, but only a segment or so after the power supply returns on leaving an area of Anti-Magic. Of course, if the spell was one cast from an item, it acts like any other cast spell, and simply collapses, with no item at the center to maintain its structure.

There are planes where memorization is unnecessary, and a mage can cast any spell that they know, subject to a maximum number of spells per day which matches the maximum number which can be memorized at once on conventional planes. (This sort of freedom is more commonly found among clerics of major local religions, where the spell is supplied by the cleric's deity when it is asked for in combat, rather than being granted earlier during prayer and stored and subsequently cast directly by the cleric. On occasion deities who do not, presumably, have the time or inclination to do this for all their clerics may grant this as a special  boon to favored high priests, or during a particular quest or temple defense or holy war.) On most such planes it is possible to memorize spells, and prudent to do so if you expect to be traveling off-plane, but not necessary. This can be extremely useful, as it avoids the difficult decisions as to which spells to take, and avoids the necessity to spend a great deal of time memorizing spells before (and during) adventures, usually much to the relief of the non-spellcasters in the party. However, there is a hidden disadvantage: in a rapid combat, the mage will find it even more difficult to decide which spell to cast, and may end up doing nothing, or something over-ingenious. This can be a particular problem for those high-level, high-intelligence mages fortunate enough to know a great many spells, especially since high-level combats tend to be decided quite rapidly. If visiting such a plane, some mages may find it advisable to memorise spells as usual, rather than disrupting their well-practiced combat reflexes. Out of combat, it is a great boon, noticeably increasing the mage's flexibility, and thus their power. Another advantage is that, since a mage does not need to consult their spell book to memorize spells, it can be safely left at home, rather than being risked to the vagaries of weather, river crossings, thieves, and fireballs on long adventures.

Why is this possible? To my knowledge, little research has been done on the subject, but presumably on such planes it is sufficiently much easier to assemble the structure of a spell and make the contacts to other planes necessary to power it, that the specific spell need not be memorised in advance, and merely the words, gestures and substances normally used to trigger the stored spell are sufficient to create it as well. The mana necessary to establish a mana flow from other planes to power the spell evidently comes from the mage (thus the maximum number of spells per day). Recovering this mana happens during sleep/rest/meditation on most planes. On some others, as well as sufficient sleep, some form of meditation or study is necessary, sometimes with the mage's spell book, for the same period as would be required to memorise the spell: on such planes evidently the mana to cast the spell must be laboriously assembled and stored, but the structure of the specific spell to be cast does not. On some planes the mana recovers slowly over a 24 hour period, partially (as is the case for psionics) or completely independent of the mage's other activities. I have even heard of planes where the mana recovery happens at some specific time, such a dawn or midnight, though this is much more common for clerics (where it is evidently a book-keeping convenience imposed by the cleric's deity, as it often differs between religions).

• Spell casting cannot be done while prone or crouching if there is a somatic component. • Spell casting negates dexterity bonuses to AC during the time of casting. During the earlier and later segments of casting dexterity applies. • No spell may be cast if the spell description is not in front of the player, and the caster states his intention and target at the beginning of the round. • Spells do no more than what is listed, and where there is room for interpretation, the DM, not the player, determines the interpretation. • Also note that characters who are spellcasting lose all dexterity bonuses while they are doing so (this is not an addition to the official rules, but a reminder of them).