I have discovered I am better at retrofitting the existing B/X classes to S&S tropes instead of developing new classes. The Thaumaturge class is just a reflavouring of the cleric. I am still debating whether this could be the default Sorcerer class. Some of the weaknesses are taken from the excellent Zefrs which I should have included with BoL and T&T in my list of games to use to run a S&S game.
Thaumaturges are those those who have dedicated themselves to some otherworldly being such as a demon or a Cthulhu-esque being from another dimension.
They will always be working towards their own advancement and the benefit of the entity which they serve. As a Thaumaturge advances in level, he or she is taught various rituals by the entity which they serve in return for the Thaumaturge's dedication and other gifts/bribes/sacrifices (to be left up to the DM). However, a Thaumaturge does not receive any rituals until they reach 2nd level (and have proven their dedication/sold their soul/etc). The prime requisite for Thaumaturges is Wisdom. A Wisdom score of 13 or greater will give the Thaumaturge a bonus on earned experience points.
RESTRICTIONS: Thaumaturges use six-sided dice (d6) to determine their hit points. They may wear any armour any may use shields. They are not extensively trained in combat and may only use weapons which do a maximum of 1d6 damage.
SPECIAL ABILITIES: A Thaumaturge may use rituals which are the same as cleric spells. However, only the reverse of any reversible spells may be used. For example, cure light wounds cannot be cast but cause light wounds can be, darkness instead of light, etc.
When a Thaumaturge reaches level 4, 6, 8 and 10, they roll a d12 on the following table due to the strain of contacting the otherworldly entities and the channeling power meant for no mortal.
1. Animal Aversion - the Thaumaturge is inherently unsettling to animals. Any natural within 10 feet of the Thaumaturge instantly becomes nervous, skittish and irritable.
3. Color Blind - Inability to distinguish one color from another. Any task requiring identifying items by color is impossible. It may also have some negative social consequences, such as an inability to put together an tasteful set of clothes.
4. Disfigurement - Disfigurements are often strange warpings of the body such as shrivelled limbs, bizarre scarring, eye discoloration or loss, transformation of hands or feet into claws or hooves, and so on. Disfigurements are permanent and always blatant, but can be hidden with some work. Characters with disfigurements also suffer some social disadvantages.
5. Distrusted - an unshakeable aura of untrustworthiness. Long hours of probing arcane secrets have subtly warped his personality and demeanour. The Thaumaturge, or even a group including the Thaumaturge, suffers a -2 penalty to Reaction Rolls.
6. Endurance Loss - Study of the dark arts has sapped your character's physical and psychic vigor. Lose 1d4 from Constitution.
7. Phobia - Fear of something. When exposed to his phobia he must roll over his level on a d12 or give in and do anything to get away from the source of his phobia.
8. Glutton - A glutton eats at every opportunity. His resultant girth means he can only wear custom-made clothing and armor, and he is of course much heavier than most other people.
9. Obsessive - The Thaumaturge is obsessed with something. When exposed to his obsession he must roll over his level on a d12 or give in and do anything to gain the obsession.
10. Nocturnal - When the sun is down, he is full of energy and will not sleep. By day, he is lethargic and groggy if not actually asleep. He is dazzled by sunlight, so much so that he suffers a -1 penalty for saving throws and "to hit" rolls.
12. Madness - The terrible secrets your character has unearthed in his quest for forbidden knowledge have begun to loosen his grip on reality. Every day there is a cumulative 1% chance that he will be struck by a fit of madness (so he will without fail go temporarily mad at least every 100 days). When it comes, the fit lasts for 1-10 days, during which time he will run wild, liable to do or say anything. At the end of the fit, the chance of another fit begins at 1% and slowly climbs as before.
EXPERIENCE AND LEVELS: As clerics.
SAVING THROWS: As clerics.
CHARACTER ATTACKS: As clerics.