Here is a new class for your Swords & Wizardry White Box campaigns. It is in rough draft form and the spell list is not yet complete. I suggest using a combination of Druid and Illusionist spells if you want to add it before the final draft is completed. I'll be taking suggestions and reposting it later.
Witches and Warlocks are individuals who have made some form of pact with an otherworldly entity, often a demon or some sort of fay creature, in order to gain magic powers.
Witch Progression Table
Level Experience HD BHB ST
1 0 1 +0 14
2 2,750 1+1 +0 13
3 5,500 2 +0 12
4 11,000 2+1 +0 11
5 22,000 3 +1 10
6 44,000 3+1 +1 9
7 88,000 4 +2 8
8 176,000 4+1 +2 7
9 352,000 5 +3 6
10 704,000 5+1 +3 5
Weapon/Armor Restrictions: Witches may not wear any armor, and they may only use daggers, staffs, darts, and slings as weapons.
Spellcasting: Witches cast spells at the same rate as a Magic-User; however their extra spells per day are dependent on their Charisma bonus instead of their Intelligence bonus. They also receive their own spell list.
Shapeshift: At character creation, Witches select one type of animal they may transform into. This may be done any number of times per day. The animal must be small and not terribly combat effective such as a rat or a raven.
Alchemy: Witches may brew potions in the same manner as Magic-Users, but may not create any other magic items.
Saving Throws: +2 vs Magical Effects, -2 vs Fire.
XP Bonus for Charisma: This bonus is for a high Charisma score.