I found these in AD&D2 and modified them slightly to Mystara D&D
Debilitating Afflictions
by RobinFollowing are several afflictions that affect only wizards. These afflictions can occur as a result of a curse, a side-effect of magical research, or a penalty from a wish. Assume that an affliction can strike at any time--short of a wish, there is no way a wizard can inoculate himself to prevent the onset of these afflictions. Unlike some organic diseases, suffering from one of these afflictions doesn’t render a caster immune to future bouts with one of these conditions. A spell caster who survives one of these diseases is equally as likely to suffer the disease again in the future as a caster who has never contracted the disease. Unless indicated otherwise, all afflictions can be cured by cure disease or a similar spell. Unless the affliction was a result of a magical attack or effect, dispel magic will not help.
Bertrek's Amnesia
Description: The wizard afflicted with Bertrek's Amnesia has trouble remembering all of the details of his memorized spells. Just as he attempts to cast the spell, he suddenly forgets a crucial element of its formula, and the spell fails to work. The onset of Bertrek's Amnesia is usually preceded by a day or two of mild headaches. The mild headaches persist as long as the wizard is afflicted with this condition.
Susceptibility: Bertrek's Amnesia can strike any wizard, but it seems to affect wizards with lower Intelligence scores. (5% chance +5% for each point lower than 18)
Effect; When a wizard is afflicted with Bertrek's Amnesia, he must make an Intelligence Check when attempting to cast a spell. If the check is successful, the spell is cast normally. If he fails the check, the spell is lost in a fizzle of useless energy and is wiped clean from the memory of the caster until it can be rememorized.
Curing; A full day of bed rest usually cures this condition, presuming the wizard refrains from casting spells, studying texts, or engaging in other strenuous mental activities. Without rest, the affliction can persist indefinitely. After every full day of rest, the DM rolls 1d20 to see if the wizard is cured; if the roll is less than or equal to the wizard's Intelligence score, the wizard is cured. Otherwise, the mage is automatically cured after he has been afflicted for 2d4 days.
Chronic Incandescence
Description: The wizard afflicted with chronic incandescence continually radiates light from his body. The glow is bright enough to penetrate any thickness of clothing and extends to a radius of 20 feet. The glow persists regardless of whether the wizard is resting, casting spells, or performing other actions. The onset of chronic incandescence is usually preceded by a day or two of sporadic glowing, particularly while the wizard is asleep.
Susceptibility: Chronic incandescence can strike any wizard.
Effect; A wizard with this affliction glows as if affected by a 1st level Light spell. This doesn’t affect his ability to cast spells, but he will find it difficult to hide from enemies. Cure Disease and similar spells have no effect on Chronic Incandescence.
Curing; Darkness cast on the afflicted wizard sometimes cancels this condition (5% chance). Dispel Magic has also been known to work. If Continual Darkness is cast on the afflicted wizard, he can make a save vs. magic; if he fails the check, his condition is negated. Likewise, if he fails a check against Dispel Magic, his condition is cancelled. These spells can only be attempted once each on an afflicted wizard. The afflicted wizard can’t cast these spells on himself. If these spells are unavailable, or if he successfully saves in both cases, the condition disappears in 3d4 days.
Conjuritis
Description: A wizard afflicted with Conjuritis produces bizarre and unexpected effects when attempting to cast any conjuration or summoning spell. Usually, there is no warning of the onset of this affliction.
Susceptibility: Conjurers are the most likely wizards to be affected, but any wizard who knows one or more conjuration/summoning spells can be stricken with Conjuritis.
Prognosis Effect: When a wizard afflicted with Conjuritis attempts to cast any Conjuration/Summoning spell, the DM rolls 1d20 and consults the table here for the result of the spell.
1d20 Result of Conjuration/Summoning Spell
1 The immediate area is filled with the sounds of thunder, while lightning flashes overhead. The thunder and lightning persist for 1d4r, but have no effects on the characters or their abilities.
2 A plush toy animal 10d4’ high appears in an area in front of the caster. The toy animal can be a Rabbit, a Dragon, a Cow, or any creature. The toy animal crumbles to dust immediately if it is touched or disturbed in any way.
3 12d12 mushrooms of various sizes suddenly pop up everywhere within a 10d4’ radius of the caster (even if caster is indoors). Each has an image of the caster's face on its cap. As soon as any of the mushrooms are touched, all of them crumble into dust.
4 The area within a 10d4’ radius of the caster fills with multi-colored soap bubbles. Each bubble has a facial image of the caster.
5 The temperature within a 10d4’ radius of the caster suddenly rises or drops 20º Fahrenheit. The change persists for 1d4 rounds, and then the area reverts to its previous temperature.
6 The immediate area fills with the sounds of human shrieks and screams. There is no apparent source of the sounds. The screams persist for 1d4 rounds, and then fade away.
7 The caster's flesh turns purple or green or blue or any other color or combination. The effect persists for 1d4 rounds, and then the caster's flesh reverts to its normal color.
8 The area within a 50’ radius of the caster is filled with a thin mist, light green in color or light purple or light orange, or any other color. The mist smells of cinnamon or mint or rotten fish or any other aroma. The mist dissipates in 1d4 rounds.
9 The area within a 50’ radius of the caster abruptly turns pitch black, as if it were affected by a Darkness spell. If the area was already dark, it abruptly becomes bright, as if affected by a Light spell. This effect persists for 1d4 rounds.
10 An image of whatever the caster was attempting to conjure appears 10’ in front of the caster, hovers in mid-air for a few seconds, and then disappears. If the caster was attempting a spell that did not conjure or summon an item or creature, the hovering image is of the caster.
11-20 the caster's spell works normally.
Curing; Conjuritis is difficult to treat. Dispel Magic has no effect on Conjuritis, nor does cure disease or similar spells. Fortunately, Conjuritis eventually clears up after running its course.
A wizard probably will not know that he has Conjuritis until he first experiences an unexpected result from a Conjuration/Summoning spell. After he experiences this first unexpected result, there are two ways he can be cured. As soon as the wizard casts two consecutive Conjuration/Communing spells with normal results, or four normal Conjuration/Summoning spells (these need not be consecutive), he is cured of the affliction;
Barlow's Blacksickness
Description: An extremely dangerous disease, Blacksickness causes the afflicted wizard to weaken every time he attempts to cast a necromancy spell. In extreme cases, afflicted wizards have died from this disease. The affliction is accompanied by stomach cramps, blurred vision, and nightmares. Its onset is usually preceded by several days of nausea.
Susceptibility: Barlow's Blacksickness primarily affects necromancers. It can also strike any wizard who knows and uses necromancy spells.
Effect; A wizard afflicted with Blacksickness risks suffering damage whenever he casts a Necromancy spell. When an afflicted wizard casts a Necromancy spell, he must make a Constitution Check, with the level of the spell used as a negative modifier. (For instance, if the wizard has a Constitution of 13 and casts a 4th level Necromancy spell, he adds 4 to his 1d20 roll when he makes his Constitution Check) If he passes the check, there are no ill effects. If he fails the check, he suffers 1d4 hit points of damage. Regardless of whether he fails his Constitution Check, the spell is cast normally. There are two additional side-effects of Blacksickness.
1. If the afflicted wizard suffers a total of 5+1d4 damage in the same day as a result of failing Constitution Checks required for casting Necromancy spells, he will experience wracking nightmares when he sleeps that night. Throughout the following day, he will experience blurred vision and stomach cramps, and will make all attack rolls at a -2 penalty. Cure Disease or similar spells have no effect on this condition.
2. If the afflicted wizard suffers 10 or more damage in the same day as a result of failing Constitution Checks required for casting Necromancy spells, he will immediately collapse. He will be unable to cast spells unless succeeding a constitution AND intelligence check, he cannot engage in combat, or undertake any other strenuous activities for the next 24 hours. (He can still walk without assistance, but his movement rate is halved.) It is possible for an afflicted mage to kill himself by succeeding to continue casting Necromantic spells, but every wise wizard would refrain from doing this.
Curing; This is a difficult affliction to treat. Strangely, the very act of casting the spells associated with the disease also seems to help cure it. Otherwise, the affliction can linger anywhere from a few days to several weeks.
Cure Disease, Dispel Magic, and similar spells have no effect on Blacksickness. Aside from a Wish, there are two known cures.
1 The DM secretly rolls 2d6. This is the number of reversed Necromancy (thus with reversed effects—healing instead of causing harm, destroying undead instead animating, etc,) spells the afflicted wizard must cast in order to purge his system of the Blacksickness. The necromancy spells can be of any level; for instance, if the wizard needs to cast four spells, they could all be 1st level spells, they could all be 9th level spells, or they could be any combination of necromancy spells from any level. Each time a reversed Necromancy spell is cast; the afflicted wizard must still make a Constitution Check and suffer the effects as described above. (Obviously, the wizard's health is safer if he refrains from casting more than one or two Necromancy spells in the same day.) The wizard never know the total number of spells he needs to cast to cure himself—instead, he's gradually getting better after he casts each reversed Necromancy spell. He is cured after he has cast the last required spell, and then has cast one subsequent any Necromancy spell that gives him no ill effects.
2 Blacksickness persists for 4d8+8 days. The DM should determine the length of the affliction at its onset, but not reveal the information to the wizard. If the wizard has not yet cured himself, the affliction is over at the end of this period.
Immaterialism
Description: The wizard afflicted with Immaterialism gradually fades away until his body is transparent, making him appear as if he were made of glass. In this condition, he is unable to fight, cast spells, or perform any other ordinary actions. The onset of Immaterialism is preceded by a gradual lightening of the victim's skin color.
Susceptibility: Immaterialism usually strikes illusionists, but any wizard who knows or uses illusionist spells can be a victim.
Effect/ Curing; If treated early, Immaterialism can usually be cured with cure disease or a similar spell. However, the condition becomes harder to treat as it progresses. Untreated, Immaterialism can last for several weeks. Immaterialism progresses over three distinct stages, each with different symptoms.
The affliction can be cured at any stage, but increases to the next stage if the afflicted comes under illusion magic effects while in its persistence period.
If not cured, the victim will not suffer any effects beyond this persistence period as if he would be cured, but instantly comes under the effect of the disease at the stage they are in, when the afflicted comes under any illusion magic effects again and a new persistence period is started.
In Stage 1, the afflicted wizard's skin turns white, as if it had been bleached. He suffers a -1 penalty to his Charisma, but there are no other ill effects.
At this stage, Immaterialism can be cured with Cure Disease or a similar spell; no save is required. Otherwise, it persists for 2d4 days.
In Stage 2, the afflicted wizard's skin remains white, but his body has the consistency of firm gelatine. He continues to suffer the -1 penalty to his Charisma. His natural AC is increased to 7. Because of this, some afflicted wizards allow their condition to advance to Stage 2 before attempting a cure.
At this stage, Immaterialism can be cured with Cure Disease, but the afflicted wizard must make a save vs. spells; if the wizard succeeds in his save, he resists the Cure Disease and remains afflicted with Immaterialism. Untreated, Stage 2 persists for 2d4 days.
In Stage 3, the wizard and all of his gear become insubstantial; he appears as if he was made of glass, but he has no substance. The afflicted wizard can’t cast spells, engage in combat, or take any other action aside from moving and speaking. He has a -4 penalty to his Charisma. However, the wizard is affected only by magical or special attacks; including weapons of +1 or better (such attacks are made against the wizard's normal AC). The afflicted wizard is able to pass through walls of less than 1’ (if they are not warded with lead/gold or Gorgon’s blood) as long as Stage 3 persists.
At this stage, Immaterialism can’t be cured with cure disease or any other spell short of a wish, or a Cure Disease and a Cure All cast by a Cleric of at least 28th level. If cured stage 3 persists for 2d4 days, and then returns to stage 2.