Adzel III

Adzel appears in:

"How To Be Ethnic In One Easy Lesson"
"The Trouble Twisters"
"Day of Burning"
Satan's World
"Lodestar"
Mirkheim

These six works might count as an "Adzel series." However, all but "How To Be Ethnic..." are also the Trader Team series. Replacing "How To Be Ethnic..." with "The Three-Cornered Wheel" and "A Sun Invisible" makes them the David Falkayn series. Replacing those two Falkayn stories with no less than six other works gives us the Nicholas van Rijn series. Thus, there is considerable convergence.

The six works featuring Adzel are introduced respectively by:

Hloch;
Urwain the Wide-Faring;
Hloch;
no one;
Hloch;
no one.

Thus, as far as collections go, Adzel is mainly a character of the Earth Book. And, of course, the entire future history comes together in The Technic Civilization Saga.