Author's Notes
Witches
Witches are not the historical "misunderstood folk magic users". Witches in Heroica are people who has entered a pact with a demon. They do it out of desperation, out of powerlessness or out of thirst for vengeance, but they are usually weak people, searching for an easy way to power. Some even do it out of good reasons, but the nature of the deal will always corrupt their intentions.
This is heavily inspired by the Palladium RPG witches. I do recommend Palladium for the world, it has some really interesting things. The rules are crap (or at least extremely outdated, and was outdated even when it was released, 40 years ago), though, so use something else if you intend to play it.
Since witch power requires no skill, no training, no talent, it is enticing to people who lacks those. Just enter an agreement, and you get power.
Of course, it is never that easy.
The pact binds them completely. The exact terms may differ. It may be for life, it may be until they have given their firstborn to the demon, it may be something else. As long as the pact remains in power, they are the slaves of the demon, and must obey them in everything. The demon, in turn, gives them some power, usually to carry out the evil orders of the demon. The demon does give enough slack in the leash to allow a glimmer of hope, then delights in jerking in taught.
Familiars fit into this concept. They are helpers, but first and foremost, they are the spies of the demon.
In Heroica, witch hunts are common, and fills a purpose. Witches let demons influence our world, and spread their evil. That said, don't expect witch hunts to be fair or reasonable. Fear is a dangerous motivation.
While witches are deeply problematic, a repentant witch trying to find a way to break the pact could work as a player character. A struggle of wills, having to do the bidding of the demon, while trying to subvert its orders, while always looking the the crack in the contract, the mistake made by the demon, the demon failing to live up to his part of the deal. Of course, that would be at the cost of the witches power, but, by then, that would be a blessing.