Fantastic Heroes & Witchery has crazy number of classes. There were so many to choose from and this is even given the fact that there is no "cleric" class to speak of. I wanted to address this and talk about the Wiseman/Wisewoman and maybe I still will, later down the road. But today I want to focus on the Occultist.
The Occultist is a magic-using character that ends up having a lot of dealings with various fiendish creatures. The class is one of the "Weird Tales" era classes presented in the book, but there is no reason it could not be used with other dungeon crawling types of classes. It is not the strongest character on the block and it's spell selection and use is a little limited, but it has some nice features.
To begin with the Occultist will be the undeniable expert on anything fiendish. Demons, Devils, whatever your world has, they will know about it. They can add their level to any skill check involving demonic/fiendish lore. This applies to any skill. The example given are survival checks when crossing a hellish-plane or a charisma check when dealing with demons. Not too shabby really.
At third level then even get secret knowledge of the demon slayers to aid them.
As the occultist gets higher levels they can even banish a demonic creature al together. Much like a cleric turning undead.
But all of this comes at a price. The occultist is tainted by corruption. The abyss staring back at you.
As they earn higher levels they have to make a Wisdom save vs. corruption or move closer and closer to chaos. A nice idea really.
Occultists learn spells from books or other occultists. But unlike wizards they do not have a number of spells per level they know, but rather a total number of spells and the highest level they can learn. So a 7th level Occultist knows 7 spells and the maximum spell level of 4th. Of those seven spells all can be 1st level or some other mix. It depends what the occultist can find in their travels.
Personally I would modify that up based on Intelligence, but that is me. The Occultist uses "Black Magic" spells, but I wonder if starting occultists could get away with using Grey magic too. At least until they fail more saves and become chaotic.
In many ways this spell casting system is the same as what you see in the Witch from The Complete B/X Adventurer. There are in fact many similarities in tone and the manner in which they get spells. I can see some overlap in these classes.
Which gives me an idea.
Skylla, 7th Level Occultist
Hit Points: 20 (d4)
AC: 4 (Ring of Protection +1)
1st: Dark Lore (+7 to fiend-based/related skill checks)
3rd: Secret knowledge of demonslayers
6th: banish fiend 1/day
Maximum Spell Level: 3rd
Number of Spells known: 6
1st Level: Read Magic, Cause Fear, Chill Touch, Find Familar
2nd Level: Black Lightning
3rd Level: Bestow Curse
Not bad, I only gave her the minimum spells, but she would likely have more secreted away in a tome for later learning.