None of the worse or bad of society ever really fades, though the move to Space did see some changes and mutation due to distance, due to who and how they could recruit, set up and how to hide better.
Head of the Guild is the Grand Master. He or she controls the whole of the organisation, which spans across Terran and Imperial space, they only have contracts in Confederacy.
They have chapters on various planets or Districts that are run by Chapter-Masters, who take on apprentices and has a string of Journeyman and a few who are Master Assassin though not in charge of a Chapter.
Next level, below are simple Master Assassin who have a drop box point that allows them to take jobs or put forward names to join the Guild.
Assassin Guild is a shadow organisation that uses drop box points to get jobs. They are not political in any way, a job is a job. They often believe they are additions to Justice in gettting those who are untouchable.
They are paid in gold, gems and in some cases Jolt. They have variety of compounds spread over both Imperial and Terran space, and two in Confederacy.
No one but the Grand Master knows how many are part of his guild, as to their wealth they are well paid for their jobs they do.
The Guild was formed as a response from the migration to the Space, the manner in which they once might have been organised no longer fully worked. The Dark Web, though not that public was unable to support their move to the starts (Human that is), so the response was to form a Guild of old. They, and their Brothers Thieves took a leaf from History and formed a Guild for their respective trades. The trinary of distance was a constant struggle for them, to get the job, travel to the jobs, and then to get away again without getting caught.
The Guild formation saw them adopting a code and means of training that once had often been done by individuals now became a organisation though with only a Grand Master who fought the last to get the job. The Guild had many teething problems, though the documents are not public, as they established their order and means of who, what, why and manner of carrying out their vocation and who or why they would not take or accept a job.