This method to erode the Mind Palace with the Mind Plague divine ability is a secret and alternative method that telepaths have discovered to have the potential to help them gain control of the Mind Palace. Some demigods don't even know about it, much less Legends.
Of course, despite being secretive about it, no one has succeeded in it. This is because other telepaths block the progress of anyone trying to take control of the Mind Palace through his method.
Every demigod implants their Mind Plague into the virtual flesh and uses it to attack the Mind Palace. The eroded part automatically falls under the control of the telepath, so this method is a faster way to gain control of the Mind Palace instead of accumulating virtual flesh.