Where It Begins

Those six opening stories (see An Intermediate Period) introduce considerably more than stated, although I have itemized all this in previous posts:

although Falkayn's and Adzel's later partner, Chee Lan, has not appeared yet, her home planet, Cynthia, is mentioned twice;

Falkayn's home planet, Hermes, and Adzel's home planet, Woden, are mentioned even before they are;

there are references to Gorzun and to an Alfzarian;

we are introduced to the idea of metropolitan "Integrates" on Earth;

the planet Ivanhoe, where we first see Falkayn, will reappear;

other significant planets will turn out to have been discovered during the Grand Survey.

There may be more. I doubt whether any other future history series has such a substantial foundation.