This organisation has either created or managed to take control of every terrorist/rebel group in CHG space and coordinated them to work as best as possible against the CHG without the underlings of these terrorist/rebel groups having even the slightest clue that they were on the same side as groups that, in some cases, had completely opposite ideals to them. This organisation simultaneously took hundreds of billions of hostages, along with massive quantities of money, and released almost every CHG secret in existence to the public to the public both at once. Yikes.
The truly incredible thing about the organisation was this: most of the people within it wanted to kill one another. The common goal was a takeover of the CHG but opinions differed so greatly between members as to what to do after gaining control and this meant that Mary Larisse being able to keep the organisation together, even if through intimidation, assassination, bribery, manipulation, blackmail, threats and even meticulous plans that often had war crimes woven into them. Even with the fact that they'd have to go with the ideals of whichever of the terrorist groups won the civil war, they all wanted to shift things from their to their own ideals. Either way, Larisse's tactic was simple: go with whoever wins, kill anyone opposed to them, be in charge.
Mary Larisse -> her inner circle (others within the organisation are unaware that Mary is in charge and believe there to be a council) -> Informants and assassins -> Group leaders (of rebel/terrorist groups) -> grunt bodyguards and labourers/technicians. It doesn't matter that much who you are in the organisation because Mary Larisse probably has explosive nanobots disguised as red blood cells flowing inside of you and, even if she doesn't, can still ensure your death.
Taking over the CHG. For each individual, the plan from there is to try and shift things towards their own ideology, usually with at least some assassinations being planned as part of it.
Hundreds of billions of hostages in the Horus Ring, tonnes of cash through ownership of both legal and illegal enterprises, as well as the fact that they borrowed tonnes upon tonnes of money in the names of their hostages and then took the money that the hostages already had as well, weapons, control over all the other terrorist organisations, informants within the CHG, numerous assassins, etc.
The organisation began as a group within the CHG that wanted to commit a coup but they were faced with a slight problem: the military was split into lots of parts and they couldn't take over all of those parts. Mary subtly took the helm and redirected them towards starting a many-way civil war to take over the CHG by making sure the CHG was one of the sides that lost and then simply inserting themselves as the leaders of the winning side.
Many were opposed to this. After all: "But what if the Communists win when I want a hyper-capitalist state?" Mary solved this through giving separate promises, swaying them to her neutral stance, manipulating them to the point where they cared more about pleasing and being of use to her than their ideologies and, where those and other "peaceful" tactics failed, assassination. Over time, those that were actually there out of ideology either forgot about what they first joined for or died. It was much easier for Mary to work with those who were there for revenge, power, money or other selfish reasons.
Terrorist and rebel groups were created on many planets with GTO members, or those who could be manipulated by them, as their leaders. Already existing groups were infiltrated and brought under the control of the CHG. Then, for a period of 3 years, almost all terrorist and rebel activity in the CHG stopped. The CHG assumed this was due to a recent bust in which 53 terrorists were caught and then tortured to death on live television by CHG executioners and how it discouraged terrorists. In truth, terrorist numbers grew as the GTO drip-fed CHG secrets, acquired from the GTO's position within the CHG itself, to many individuals to make them join these groups.
At the end of those 3 years, the CHG legalized and released the software for public private VR use (allowing companies to create programs such as games, whereas all previous programs had been state-made and for things like education and healthcare) within the Horus Ring. That same day, everyone wearing a VR headset within the Horus Ring was trapped in their headsets, ridiculous amounts of money were borrowed in their names from banks, and then all that money went straight to the GTO. At the same time, tonnes of CHG secrets were released onto the internet, VR net and all the other nets, with powerful encryptions that prevented the CHG from taking the websites hosting these secrets down or blocking them. A day later, the GTO would remove the ability of the CHG to see who looked up what, making them unable to use fear tactics to prevent people from looking up the secrets within.
The GTO then used the money to buy tonnes of weapons off of the Blue Army General, but decided to shoot him in the head and take the goods rather than pay him, making sure to reveal his actions and those who had helped him with them in the process to further discredit the CHG.
These weapons and ships and so on are distributed to the terrorist groups, which have already been building up weapons supplies, and the madness begins.
Their existence was discovered and, with that, the members of the organisations they controlled killed their leaders and installed new ones from within their ranks, leaving the GTO unable to control any of what happened in the war except by re-infiltrating the rebel organisations, which were now acting on their own and even against one another. From there, their numbers were worn down by cases of them being discovered and killed, abandoning the GTO, etc. The remaining members, including Mary, were killed at a conference with CHG leaders, along with said CHG leaders, to make a deal with regards to bringing about the submission of the Rim Worlds (who had declared themselves independent and formed a confederation).