While they can engage in sexual activity at any time, Exekians are only capable of producing offspring once every 240 years. Thus, in the days of the Old Exekian Empire, time was measured in eras, which lasted 240 years and marked each reproductive cycle.
Due to the many wars between humans and Exekians in the mere 200 years since the Revolution, the population of the species has plummeted drastically, with no new Exekians being born to keep the balance. The last kluuda resulted in only a few hundred successful births. Despite their immortality, the Exekians are on their way to becoming extinct.
For the first 240 years of their lives, Exekians are not typically sexually active. In this way, although they mature physically and mentally much more rapidly than a human, sexually they progress far slower.
Upon reaching their 240th year, however, they experience dramatic changes. Kluuda first reduces their physical strength and reaction times, making them weak and sluggish. This is followed by fever, raising their body temperature to abnormal levels. This eventually becomes sporadic, but the intense and irresistible urge to mate that comes with it dominates their every thought. It is thus deemed necessary to mate with as many people as possible, as often as possible, until the end of kluuda. A single Exekian male can father several children in one cycle by numerous females.
During the mating process males go into a trance-like state, becoming more "docile"; this is to keep them from moving and causing harm to themselves or their partner. The male injects sperm directly into the egg of the female. The female then lays the egg in the male, who carries it for approximately a month before giving birth to a chrysalis. The chrysalis is kept in a cool, wet environment (usually a cave) until it hatches, usually within a few weeks.