Maximum AC- 12 / Minimum Starting Hit-Points- 4
You are of the lowest caste, born into your wretched life, or you were dropped here for catching an incurable disease or breaking a church vow (in many parts of the world, these go hand in hand). The Untouchables are the street cleaners, sewer washers, rat catchers, and chamberpot maids. The highest position one can aspire to be as an untouchable is a torturer or executioner; as their contact with human blood and tears makes them unseemly. These positions are also highly coveted by untouchables, as many among the ones who you'll kill will be of higher caste then you.
Untouchables are always dirty and a pin's drop from being ill at any moment. You may catch any disease you wish, as long as a contained person or vector exists. You still suffer all the negatives of having the disease, but this lets you catch diseases that are magical or hard to catch in case you want to be a science experiment. For example, you can catch vampirism by rubbing the dust of a slain vampire into your burst pustles on your face, or catch lycanthropy by sucking the marrow from a long dead wolf bone. Against most diseases that you don't actually want, just get +2 to saves vs disease.
At 2nd, 4th, and 8th level, you get +1 damage to all attacks. Against those of significantly higher birth status then yourself, such as Kings or Temple-Priests, double this bonus.
At 1st, 3rd, and 7th level, you get +1 to all stealth rolls. You're sneaky when you don't have a cough.
At 5th level, your maximum AC increases by +1. You also gain the ability to desecrate a sacred site or object, which makes its power shut off or significantly weaker. Technically all you have to do is touch it to do this, though most untouchables will spitefully spit, bleed, or shit on the object in question. Objects that are desecrated are either permanently soiled if minor in power or importance, or must be ritually cleansed if major in importance. For example, a desecrated holy symbol will not be able to turn undead, until it is purified. Note that “purified” does not mean “cleaned”. You could shit on the steps of the church, wipe it off, and the priests will still cower in it when the hoard of zombies come, unknowing that the holy spirit that protects the place has been silenced.
You also have the ability to carry a disease with you. For every disease you choose to carry, you continue on with life with a lesser batch of systems and -1d4 maximum hit points. If the disease is terminal, you will instead only live for 1d6 years if you choose to carry it. Carrying a disease means you can still infect others, but you are spared from the worse effects.
At 10th level, you become a Wretch. You can now willingly exude any disease you carry as a miasma cloud, which acts as a save or be infected attack- this cloud pours out of your mouth and is affected by the wind. It is also purified by sweet smelling things, which is why plague doctors wear perfumed masks. You draw followers to you whenever you decry a public official or take responsibility for desecrating holy things; a group of 2d20 city urchins, hobos, and unwashed become your loyal followers. They may be willing to do things for you, but they obviously have no money.
Additionally, when you die you will rise again as a 2 HD undead Plague Ghoul. If you died via lawful execution, make it a 3 HD Plague Ghoul. Your followers will still be loyal to you.