Episode 26 of The Trigan Empire
The City of Jewels
aka The City of the Jewels
The Zargot Fighter
Het geheim van de eeuwige jeugd (Dutch title)
The Secret of Eternal Youth (Dutch title, translated)
The City of Jewels was originally published in 9 installments in issues 480 (3 April 1971) to 488 (22 May 1971) of Look and Learn magazine.
It was reprinted in the 1977 Vulcan Annual.
It is reprinted in the Don Lawrence Collection Volume 7, The Rallu Invasion.
Plot summary (Dutch)