Original "Star Trek" fans refer to this as the "Return to Voll" episode because it features Keith Andes who played Akuta in "The Apple", the one where the Enterprise crew lands on a planet where the natives worship a computer in a cave. You probably won't recognize him but his voice is very distinctive.
It is also known as the "Moon" episode after William Smith's memorable performance as the bad biker leader in "C.C. and Company. After playing good guy Joe Riley in "Larado", Smith became the quintessential television and "B" movie bad guy. In "Buck's Duel to the Death" Smith plays an evil alien warlord called "The Traybor". In addition to his trademark size he is wired to direct a surge or bolt of electricity toward his opponent. Smith's acting style is basically copied from Jack Palance.
Buck is recruited by Darius (Andes) to rescue his daughter from the Traybor's harem. Although Erin Gray only appears in a supporting role, "Buck's Duel to the Death" still manages to be the most scenic episode of the entire series with respect to beautiful actresses. Darius has two nice looking daughters (one played by Robert Stack's real-life daughter), The Traybor has a hot evil sweetheart and about a half dozen assorted harem beauties.
It is not one of Smith career highlights, he was getting a little long in the tooth by this point. And the humor (the saving grace of the first season) is in very short supply.
Then again, what do I know? I'm only a child.