In the distant past, well before the formation of the Dragaeran Empire, the Jenoine colonized Dragaera. The planet was already inhabited by the native Serioli as well as by some Easterner colonists, whom the Jenoine captured and used for genetic experiments. Sethra Lavode asserts that the Dragaeran race are, in fact, descended from Easterners modified by the Jenoine. The Jenoine also crossbred various animals with Dragaerans, creating the thirty-one Tribes that later became the seventeen Houses. They engaged in various experiments with animals, one of which resulted in the development of sapience in jhereg.
It says something about the Jenoine's power that their former servants and assistants are among those now known on Dragaera as the gods. Eventually, a combination of internal struggles within the Jenoine and sabotage by some of those servants, including Verra, resulted in an explosion of amorphia that created the Greater Sea of Chaos and destroyed all the Jenoine on Dragaera at the time. Ever since, the Lords of Judgment and various others have worked to prevent the Jenoine reappearing on Dragaera.
The Jenoine appear as roughly humanoid creatures, about nine feet tall, thick and robust, with no hair or visible sexual characteristics. The times we have encountered them, they didn't wear clothing. Their robust torsos seem to contain redundant copies of vital organs, and they're known to regenerate when wounded. They each have two very widely-spaced eyes that remind Vlad of fish eyes, and remind Loiosh of something else. (Issola, Chapter 4, Chapter 6)
They are highly-resistant to the effects of amorphia, and cannot be easily killed by conventional or Morganti weapons. However, the Great Weapons can destroy them. (Most notably Godslayer, against which they may have no defense.)
- One Jenoine partially manifested during the Battle of Adrilankha in Sethra Lavode, and was able to temporarily neutralize the Orb (and in addition, greatly enhance the power of Orlaan).
- One Jenoine "redefined the defenses" of Dzur Mountain, approximately concurrent with the events of Taltos, although not recorded there. Sethra Lavode defeated the Jenoine, but not without help. See also:
- Several Jenoine kidnapped Aliera e'Kieron and Morrolan e'Drien, plotted to drain and use the Lesser Sea of Chaos, and later showed up by that Sea and physically fought an army of the Gods, described by Vlad in Issola.
In addition to the above, in Issola, Verra mentions that there were attacks by the Jenoine on the Greater Sea of Chaos, the Halls of Judgment, and the Imperial Palace (which may be a reference to the neutralization of the Orb, see above), all of which were successfully resisted.