Firstly, they're essentially wizards, though you do need to specify 'Witch.' The only difference is how their magic dice work.
I was very largely inspired by http://chaudronchromatique.blogspot.com/2016/05/hagborn-character-class.html so go read that. It's doing something different than what I'm doing but its cool.
The deal with a Witch is that they have INFINITE MAGIC DICE!!! The downside is that they age [sum-Level] years of age whenever they cast a spell. They get an extra 'level' for old age calculation if they take double time to cast a spell.
This means that witches prefer to cast small, slow, careful, cantrippy spells in their day-to-day lives, but if you piss them off royally they can unleash unholy cans of curse-ass that wizards simply can't rival. So that fits my idea of them being reclusive and prone to using herbalism and countercultural common sense to advise whatever small village they live in/near rather than spells, but at the same time nobody wants to get on a witches bad side, not even squads of trained warriors. But kings and such don't want them around because of their mishaps and cultural baggage.
As an unintended but not unwelcome side effect, this also means they have no reason to wear silly magic robes for extra magic dice. While noncombat witches may dress as a classic witch for effect, or simply stick to sensible, comfortable clothing, combat witches could strap on a full suit of plate and be just as magically potent. And I'm fine with this, because this marks another divide between them and wussy academy wizards. Battlewitches, hell yeah.
|But inside is an elderly lady who's sick of your shit|
The mishaps from Witchery make it hard for normal folks to look kindly upon them. As the witches are actually drawing on their own life force as much as they can, this feels very unfair, but sometimes the spells just damage or warp the life force of others.
1-Mutation, save or it is permanent. If any pregnant things are nearby, a random unborn child gets the mutation instead. Yes, you are allowed to cart a pregnant goat around to act as a lightning rod, but you have only yourself to blame when it births an honest-to-glog Monster with a capital M.
2-Toads, snakes, and worms spill from mouth when speech is attempted for 1d6 rounds.
3-Nearby milk spoils, wine sours, etc, and a random target fails their next save.
4-Animals save or get scared and angry. Horses flee, dogs probably bite the witch. Cats immune.
5-Rainclouds show up and rain on witch for 1d6 days. Rain is mildly acidic and doesn't nourish anything but swamps, will kill crops.
6-Nearby being saves, or is stricken barren/sterile.
Luckily(?) witches have no dooms. The rapid aging sure to occur from using their full power incautiously is doom enough. And unlike lecauldronchomatique, the age of these witches is only one-way- no eating babies to fend off old age, no matter how much you may want to.
It takes a long time (or the Cantrip Trait) to be able to cast spells safely, but I think players might appreciate the idea of being an intelligent character who views spells as their last choice, rather than their first, but has a trump card hidden away in case things get bad.
Note that you don't have to be a witch to cast spells in the Witch fashion, but you do have to be trained by a witch, and you won't actually have witch levels so you'll shrivel up and die of old age only slightly slower than that Nazi from Indiana Jones III.
|'Local Heleognostic not so tough after culturally appropriating witch secrets'|
Witches can draw on other people's life forces. Sacrificing sapient beings during spellcasting blocks an extra 1d6 years of age loss, +1 if they're a baby or something. With this option though, I don't think the Witch-Queens would have lost the war, I think they and their altars of blood-sacrifices would still rule over the land in Aztec fashion and the motto of the land would be 'It takes a witch to stop a witch.' Witchpunk!