From Hashshashin Wiki
This campaign uses The Riddle of Steel Rules, and is designed to be played largely as a solo campaign. Though, we do have several players, many of the adventures, at least for the first portion of the campaign, are designed to be taken on solo. But because of the way the campaign was designed, players are still able to play in groups if the situation finds itself there. And upon arrival of the second portion of the campaign, group play will not only be easier to to run, but it will be quite a bit more fun. And upon reaching the third portion, almost anything will be possible.
While it is noted that the campaign will be using TRoS rules, it should be noted that the Seneschal's TRoS rules differ in some ways from the traditional TRoS rules in the books. Therefore, one should reference the TRoS Wiki when looking up specific rules or standards. And also note that there are some Specific Rules that will be used in this campaign exclusively, like the Drama Rewards system.
The Historical Hashshashin, the pseudo military arm of the Nizaris people in the modern-day Middle East, were sleeper commandos and assassins who used their skills to protect their people and maintain a political balance between their enemies, allowing the Nizaris people to prosper for over 150 years.
The Setting for our campaign takes the concept of the historical Hashshashin and gives it a Western European twist. Still an ancient organization of highly trained assassins, still working to maintain the balance of power in the land, but now in a Medieval Europe setting. Using the standard TRoS world of Weyrth, the campaign takes place in a Remote Mountain Stronghold in the nation of Cyrinthmeir, where the player characters are just learning about their new life as future assassins.