(Note: there are differences between the original version (Dragon 38), and, the version in Best of Dragon, Vol. V. This is the version from Dragon 38.)

In TD #19 (Vol. III, No. 5) there was a very useful article by Steve
Miller entitled "Spell Determination for Hostile Magic Users, or Why
Did He Throw That Spell?!" As the title indicates, this article contains
charts for randomly rolling up which spells non-player MUs used,
without the referee having to make arbitrary decisions about it. This
worked fine for a while, but soon a couple of problems arose. For one
thing, the AD&D Players Handbook was released (certainly no
problem in itself!), containing a variety of new spells which should be
included in the list of spells "possibly used by hostile MUs." Another
problem was in determining the level of the spell the MU would use:

Though Steve?s system worked fine for some levels, there were other
levels (especially when MUs got an odd number of spells) that simply
couldn?t be rolled up exactly. At ninth level, for instance, a MU gets firstto fifth-level spells, four, three, three, two, and one respectively, for a
total of thirteen spells. I can think of no way of generating the numbers
one to thirteen, except possibly with cards.

Thus, I give you the new system (below) which follows much the
same pattern as Steve's system, but uses percentages to find what spell
level is used (thus giving a more exact chance of using any particular
level).
* * *
 

SPELL USE BY MAGIC-USERS
                                                                                                                                        Level of spell used**

Level	Chance of  spell use*	1	2	3	4	5	6	7	8	9
1	64	01-00	-	-	-	-	-	-	-
2	66	01-00	-	-	-	-	-	-	-
3	68	01-67	68-00	-	-	-	-	-	-
4	70	01-60	61-00	-	-	-	-	-	-
5	72	01-56	57-84	85-00	-	-	-	-	-
6	74	01-50	51-75	76-00	-	-	-	-	-
7	76	01-40	41-70	71-90	91-00	-	-	-	-
8	78	01-34	35-59	60-84	85-00	-	-	-	-
9	80	01-30	31-53	54-76	77-91	92-00	-	-	-
10	82	01-27	28-54	55-74	75-87	88-00	-	-	-
11	84	01-22	23-44	45-66	67-83	84-00	-	-	-
12	86	01-20	21-40	41-60	61-78	79-95	96-00	-	-
13	88	01-20	21-40	41-60	61-76	77-92	93-00	-	-
14	90	01-19	20-38	39-57	58-72	73-87	88-97	98-00	-
15	90	01-18	19-36	37-54	55-72	73-90	91-97	98-00	-
16	90	01-15	16-30	31-45	46-60	61-75	76-87	88-96	97-00
17	92	01-15	16-30	31-45	46-60	61-75	76-85	86-94	95-00
18	92	01-15	16-30	31-45	46-59	60-73	74-82	83-91	92-97	98-00
19	92	01-14	15-28	29-42	43-56	57-70	71-79	80-88	89-97	98-00
20	94	01-14	15-28	29-42	43-55	56-68	69-79	80-87	88-95	96-00
21	94	01-13	14-26	27-39	40-52	53-65	66-75	76-85	86-95	96-00
22	94	01-12	13-24	25-36	37-48	49-60	61-72	73-82	83-92	93-00
23	95	01-12	13-24	25-36	37-48	49-60	61-71	72-82	83-93	94-00
24	95	01-12	13-24	25-36	37-47	48-58	59-69	70-80	81-91	92-00
25***	95	01-12	13-23	24-34	35-45	46-56	57-67	68-78	79-89	90-00
26***	95	01-12	13-24	25-36	37-48	49-59	60-70	71-80	81-90	91-00

*--This is the percent chance that the MU will even use magic-he
may decide to use his trusty dagger or some other weapon. This
percentage can be modified according to the situation, at the DM?s
discretion. Remember, most intelligent MUs won?t usually attempt to
cast a spell if they are under direct attack and the chances are too great
they will be hit and the spell ruined.
**--As mentioned above, this percentage can be modified according to the situation. For instance, an MU would more likely cast a
high-level spell at a large group of powerful opponents than a small
group of relatively weak ones.
***--Fortunately, the spells gotten per level begin repeating a
pattern here so the percentages will always be the same for odd
numbers above 25 or all even numbers above 25.
Once the spell level has been determined, percentile dice are rolled
to see which spell on the chart below is cast.

First Level

01-08	Burning Hands
09-18	Charm Person
19-24	Dancing lights
25-28	Detect Magic
29-34	Enlarge
35-42	Friends
43-48	Hold Portal
49-52	Jump
53-62	Magic Missile
63-66	Protection: Evil/Good
67-76	Shield
77-84	Shocking Grasp
85-94	Sleep
95-00	Ventriloquism

Second Level

01-06	Audible Glamer
07-12	Darkness, 15' r.
13-17	Detect Evil/Good
18-22	ESP
23-27	Forget
28-36	Invisibility
37-43	Levitate
44-50	Mirror Image
51-55	Pyrotechnics
56-64	Ray of Enfeeblement
65-67	Rope Trick
68-75	Scare
76-83	Stinking Cloud
84-92	Web
93-95	Detect Invisibility
96-00	Wizard Lock

Third Level

01-06	Blink
07-10	Dispel Magic
11-14	Feign Death
15-24	Fireball
25-28	Flame Arrow
29-34	Fly
35-36	Gust of Wind
37-42	Haste
43-50	Hold Person
51-54	Invisibility, 10' r.
55-58	Leomund's Tiny Hut
59-66	Lightning Bolt
67-72	Monster Summoning I
73-80	Phantasmal Force
81-82	Protection: Evil/Good 10' r.
83-88	Protection From Normal Missiles
89-94	Slow
95-98	Suggestion
99-00	Tongues (or Reverse)

Fourth Level

01-06	Charm Monster
07-12	Confusion
13-14	Dig
15-21	Dimension Door
22-25	Enchanted Weapon
26-27	Extension 1
28-34	Fear
35-36	Fire Charm
37-43	Fire Shield
44-47	Fumble
48-51	Hallucinatory Terrain
52-58	Ice Storm
59-65	Minor Globe of Invulnerability
66-71	Monster Summoning II
72-73	Plant Growth
74-80	Polymorph Others
81-86	Polymorph Self
87-90	Curse (opposite of Remove Curse)
91-96	Wall of Fire
97-00	Wall of Ice

Fifth Level

01-04	Animal Growth
05-08	Animate Dead
09-13	Bigby's Interposing Hand
14-20	Cloudkill
21-27	Conjure Elemental
28-35	Cone of Cold
36-39	Distance Distortion
40-43	Extension 2
44-47	Feeblemind
48-52	Hold Monster
53-56	Magic Jar
57-61	Monster Summoning III
62-66	Mordenkainen's Faithful Hound
67-70	Passwall
71-74	Stone Shape
75-79	Telekinesis
80-84	Teleport
85-88	Transmute Rock-Mud
89-93	Wall of Force
94-97	Wall of Iron
98-00	Wall of Stone

Sixth Level

01-06	Antimagic Shell
07-12	Bigby's Forceful Hand
13-16	Control Weather
17-24	Deathspell
25-32	Disintegrate
33-34	Extension 3
35-42	Geas
43-50	Globe of Invulnerability
51-58	Invisible Stalker
59-64	Monster Summoning IV
65-68	Move Earth
69-76	Otiluke's Freezing Sphere
77-80	Projected Image
81-86	Repulsion
87	Spiritwrack
88-93	Stone-Flesh (or Reverse)
94-00	Tenser's Transformation

Seventh Level

01-07	Bigby's Grasping Hand
08-10	Charm Plants
11-20	Delayed Blast Fireball
21-27	Drawmij's Instant Summons
28-34	Duo-Dimension
35-44	Limited Wish
45-49	Mass Invisibility
50-56	Monster Summoning V
57-65	Mordenkainen's Sword
66-70	Phase Door
71-79	Power Word-Stun
80-86	Reverse Gravity
87-91	Statue
92-00	Vanish

Eighth Level

01-08	Antipathy/Sympathy
09-18	Bigby's Clenched Fist
19-20	Clone
21-30	Incendiary Cloud
31-38	Mass Charm
39-45	Maze
46-50	Mind Blank
51-60	Monster Summoning VI
61-67	Otto's Irresistible Dance
68-76	Polymorph Any Object
77-83	Power Word-Blind
84-90	Serten's Spell Immunity
91-98	Symbol
99-00	Trap the Soul

Ninth Level

01-10	Bigby's Crushing Hand
11-18	Gate
19-22	Imprisonment
23-36	Meteor Swarm
37-48	Monster Summoning VII
49-58	Power Word-Kill
59-70	Prismatic Sphere
71-82	Shape Change
83-86	Temporal Stasis
87-96	Time Stop
97-00	Wish

If the spell indicated has insufficient range or is generally inappropriate (such as Detect Good/Evil in the middle of combat, using Hold
Portal when there is no door in the area, etc.) a re-roll is allowed.

Some things to remember:
Detection spells will generally only be used during the first turn of
the encounter, since the MU may wish to discover the alignment,
magical-powers, etc. of his enemies (if they are enemies)--
he is obviously not going to try to find out the alignment of someone who is attacking him anyway.

Some spells which may seem illogical at first may have some
purpose. For instance, an MU might cast Detect Invisible on the group
during the first round (or during combat if one of the group disappears)
to see if he is going to be attacked by an invisible intruder. However, if
outnumbered or on the losing end of the battle, an MU will almost
always use a defense spell (Dimension Door, Teleport, etc.) or powerful weapon spell.

On the same note, occasionally a spell may be indicated that is
inappropriate due to the level of the defenders (i.e. a Sleep spell
against tenth-level players). This will not always necessitate a re-roll,
since there is usually no way for the MU to know the level of his
opponent(s) anyway (unless, for instance, one of them casts a highdice fireball or other such level-based spell which would give him
away: it is assumed that the MU would recognize magic equal to or
more powerful than his own).

JHSII wrote:
Gary,

How did you determine what spells a NPC magic-user had in his spellbook? I need to create some spellbooks for some 7-9th level magic-users, but I don't know of a fair way to determine how many spells of each level is in the spellbook for each of them, and beyond the starting spells, which spells they will have added.
 

Thanks!!
 

Ah, one of the joys of being the GM.
If the GM can not be fair, what is the sense of having one?

All you need to do is put your PC in place of the NPC and then choose and roll for the possession of the best spells--or else simply decide four yourself and forget chance.

Cheers,
Gary
 
 

garhkal wrote:
...
What about enemy casters of the normal races. like an evil human mage... or elvin one... How did you develop their spell repotoir...?
 

Whatever is logical for the NPC, and would be most useful in attacking foes, defending against their attacks, is how I select spells and magic items--keeping in mind that the PCs might well end up with the spell books and/or items.

One needs to walk a fine line when devising antagonists for the party to face.

Cheers,
Gary