As it happens, the two Czech most prolific murderers lived about a century after the game takes place. Clearly, it would not be historically accurate to have these very people in the game, however the team may use them as inspiration.
Martin Roháč was a soldier who took part in the war with Turkey in 1566-68. After being dismissed from service, he and a couple of other soldiers started robbing and murdering people in the Czech lands. Most of their victims were defenseless merchants.
Roháč’s gang brutality was increasing. Among their final deeds was murder of three pregnant women (at three different locations). They cut out 4 fetuses out of the women, then fetuses’ hearts, lungs and liver, cooked them and ate them. The brutality was increasing to the point that the other gangmembers were gradually leaving, until Roháč was left to do his deeds alone.
Roháč was apprehended in 1571 and found guilty of murdering 57 people. He was sentenced to death by the following procedure:
First, Roháč’s fingers were being cut/torn off slowly, segment by segment. Then the executioner used a pair of pliers and started slowly tearing off pieces of Roháč’s body [in a way preventing fast death, probably with the pliers being hot in order to prevent blood loss]. Subsequently, Roháč was put on a wheel and they broke most of his bones. After this, he was left in the wheel to die.
The execution was demanding to the point that the executioner needed help of 6 assistants to be able to carry it out correctly.
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Kateřina z Komárova was a noblewoman that was left home alone while her husband was tending to his duties at the royal court. While he was away, mostly at Karlštej Castle, she was taking care of their properties at and around Pičín. [Píča means cunt and Pičín may be translated as a cunt-hole]
Kateřina became notorious for killing young pretty female subjects. She would beat them, cut their skin with iron and tear the skin down alive. She was found guilty of 14 murders, while she most probably killed at least 30 people. She was sentenced to death by hunger in 1534.

I’d say that having quests that would deal with similar people could be nice, what do you think?