The module Maze of the Riddling Minotaur indeed severely limits the use of magic AND exploration (due sight limitations).
I had devised this spell due old discussions on some D&D forum of Bygone days.
Yet nowhere it is described WHY/HOW this is so.
I know it is old, and may need some minor revisions, yet overall it does fit the module's described effects.
I hope this helps
Minotaur Maze
by RobinIt is best to be assumed this spell was created when the Minotaurs were at their peak of social/cultural/magical prowess. The spell thus survived the decline of Minotaur culture. It is rumored that Gildesh was one of its creators, yet the other 8 are still unknown (suggested; Kiranjo, Oloron which bth are rumored to be Immortal and have been Minotaur).
9th level Alteration Evocation Abjuration spell
Range: 2 Dimensional 800 x800x20 or 3 Dimensional 400x400x400.
Duration; Permanent
Effect: Special.
Saving Throw: Special
Reading time: Cant be written on scroll and contain the power needed.
Casting time ; 1 full DAY (or less see below)
Component; Verbal, Somatic, Material( one Minotaur made or possessed maze,
Example; 
AND 1 flask of Elemental Air, 1 Bowl of Elemental water, 1 spark of elemental energy(not flame), 1 crystal of elemental Matter, 1 sacrificed creature (if Minotaur see below) for Entropic energy.)
Additional Sacrifices to reduce Turning as described below. This is an Evil act.
Information; This spell causes an existing labyrinth created by Minotaurs or taken over by Minotaurs (thus not a Maze created or occupied by Humans, Dwarves or other creatures), to be affected by several very powerful magical effects. This is important as the magic affects the tiny traces left behind by the Minotaurs (fur, skincells, sweat, scent, magical residue, etc)
The spell can affect a Maze in one horizontal layer with affected Dimensions of 800 feet by 800 feet and 20 feet high, or a multi-layer Maze with Dimensions of 400 feet by 400 feet x 400 feet. Any part of the Maze beyond these Dimensions will not be affected in any way. Several effects will happen in the affected Area. (Adjusted from the Old Adventure Maze of the Riddling Minotaur).
This spell must be cast by a minumum of two caster's using this spell of which at least one is a Minotaur of any breed, or a Winged Minotaur. If this can not be done, a minotaur must be sacrificed and fully used in the enchantment while 9!! spellcasters work together to create this spell.
The spell is exhausting and has a very long casting time. If more than 2 casters are used the casting time is reduced by 2 hours for each eaxtra caster up to a maximum of 9. If a minotaur is sacrificed (willingly or not) the casting time is reduced to 12 hours, but can be reduced no more by adding additional casters. If any caster is disturbed during either variation of the casting the spell fails, and must be recast.
1 The Maze is filled with a magical swirling black fog which extends from the ground up to 20 feet high. Within the fog, all sight is limited to 20' or a single room, including Infravision, Darkvision, and any magical form of sight such as X-ray vision, See in to the Ethereal, etc. The radius of any light source or darkness effect is similarly limited to 20' or a single room(whichever is smaller), as is any magic that affects sound (such as silence or ventriloquism). These can also not be targeted on a creature. Missile fire within the fog is at -6, or -4 if a blind-shooting ability is successfully used. Second Sight gained from magical sources is also restricted, yet Second Sight from Fairies and Dragons not.
2 Maximum movement is 60 feet per round, and this is the running mode. The fastest walk rate will be 20 feet per round.
3 No Magical spell of power level 4 or higher will work, or can be cast in the affected area( thus a pre-cast spell will be come active
again when the Maze is left during the spell duration of that particular spell.
4 No Clerical spell of power level 5 or higher will work, or can be cast in the affected area (thus a pre-cast spell will be come active
again when the Maze is left during the spell duration of that particular spell.
5 Any Transportation spell will bring you 1d8x20 in any direction to open places, except out of the Maze.
6 No divination spell with an alignment or magic base will be functional (As everything will radiate magic, and the evil/good of the caster).
7 No Fear or remove fear spells or abilities can be affective in the spells area.
8 A Find Trap spell will reveal all traps within the casting/activation area for 2 Turns, to be avoided or disarmed.
9 A Silence spell will silence up to 20 maximum, but will always affect a whole room, and never a creature.
10 The Following spells and abilities with the similar effects are impossible to take effect in the affected area: Know Alignment, Remove Fear, Snake Charm, Confuse Alignment, Bless, Blight, Blindness, Cure Blindness, Disease, Cure Disease, Growth ( any form), Shrink (any form), Locate (any form), Curse (any form), Remove Curse (any form), Dispel Magic (Touch Dispel on items will work though), Alteration spells (any form), communication spells (any form). The reverse of any spell listed (Confuse Alignment, Blindness, etc.) will also fail. All other spells will work normally in the affected area. Any Invisibility cast/activated outside the area of effect of this spell still works yet can't be reactivated inside the area of effect when broken, This does not include Fairy's Invisibility to Mortals.
11 Haste Spells; The description of limitations in the module says that Movement in corridors is doubled and two attacks per round are possible, yet investigation (aka actions in a room/chamber other than movement or combat) still takes a full turn. A Slow spell will work as normal[/color]
12 No Fly, Levitate, Float in Air will work, except when it is an natural ability, like Beholder Flight, bird wings, etc.
13 No Illusions can be cast, except those cast outside the range of the spell, and then brought in.
14 A Web (or similar) spell will spread 240 degrees from the caster and thus blocking all sides, floor, ceiling, and front as seen from the caster until removed in the normal way of these spells (fire can be used to burn away web, strength and cutting can also be used...this takes aas much time as 20 minus the Strength of the PC (add the mgical bonus of cutting weapon used to the character's strength).
15 ESP will reveal the space up to 60 away from the caster but only rooms, and corridors will be revealed.
16 Clairvoyance will reveal the space up to 60 away from the caster but only visible things will be revealed.
17 Clairaudience will reveal the sounds up to 60 away from the caster.
18 Fireball will become a Hyper concentrated Magic Missile with no risks for the caster.
19 A Lightning Bolt will not Bounce.
20 The caster cant be damaged by his own spell, even when disturbed (but nothing is said of his companions near him).
21 Turn Undead is severely restricted due the evil nature of the caster. The module itself bans Turning Undead completely.
Other D&D BECMI sources in this case use various methods to restrict this by lowering the Turning Level of the turning Cleric for this purpose. Keep in mind lowering the effective Turning level also affects the range on which Turn Undead would work.
In my MMMCUndead there is a complete Turn Undead table and explanation on page 1123-1125
I reproduce the table here. My advise is to reduce the effective Turning level the maximum of 5! steps making a 29-32rd level cleric as effective as an 13-14th level Cleric, and a 15-16th level Cleric would be as effective as a 7th level cleric instead. (only in other Planes (IMset/WotIset) this maximum of 5 steps can be increased further by the distance from the Prime Plane/Cleric's Immortals Plane at the momement. Example 1st layer of Hell is 2 planes from the Prime, the 9th is 11 planes away from the Prime)
To come to an even worse Turning a further reduction due sentient Undead or Necromancer Controlling Undead can be used. As per RC canon a skeleton controlled by a Vampire must be turned as a vampire to break the control and then only a second Turning will affect the undead as normal (under the reduced Turning Level). This would reflect BECMI rules and logic more and be more consistent to the Mystara feel. In the above example of a 15-16 level cleric he could turn as a cleric level 7 at 60' maximum. and would turn a Vampire only away (not damaging) on a 9 or higher on 2d6. So in total effect very difficult. A Necromancer controlling is seen by its level and HD. As humans have (normally) a 9HD limit, Turning would be based on 9HD (almost equal to a Vampire or Phantom. For every 4 levels higher than 9th level add 1 to this referential HD and check for similarities with equally strong Undead, that will be used as the base to use Turning to brak the control. Any turning will not affect the Controller and it will only be aware of it's breach of control if seen.
Extra; You could allow a further reduction in Turning by sacrificing a highly pious non-entropic character (mostly a Paladin/Cleric of 20th level will suffice) else use Pious individuals with a piety of 100+ (see; here). For each such character the Turning will be reduced by another 3 steps accordingly. Thus if 4 characters are sacrified a 12 extra steps are used making Turning near impossible.
Keep in mind when Turning damage is given(2D6, 3D6, etc) this is in HD not hp. Normally a minimum of 1 undead is always affected, however a more powerful undead will only lose the HD and suffer pain/torment yet can still act as it wishes.
