Leviathan Canon: Sex Drives, (In)Fertility & Breeding
To prevent the multiplication of more of these terrifying beasts that were His first and greatest of triumphs, yet would inevitably tear the universe asunder and bleed it dry of anything else He created, God NULLIFIED the Leviathans’ ability to reproduce. All of them, both male and female, were made infertile.
To further block any would-be ‘miracles’ from occurring, the Creator also stripped them of their instinct to breed, as any living creature would have the natural desire to procreate and continue their lineage, whether through asexual or sexual reproduction. Leviathans had NO INCLINATION to create ‘more’ of themselves because of this lack in reproductive instinct, so even despite their inability to produce offspring, having no desire or instinct to procreate would also prevent them from seeking out or creating other possible measures that may turn out effective, in any capacity.
As all of the remaining Leviathans would be locked away in Purgatory together, both of these steps were necessary to ensure no more of these beasts came into the universe, and that their prison did not become overfilled and eventually break from the sheer OVERLOAD of its inmates. It is rumored, however, that this ‘tactic’ was not originally God’s idea, but the Lord was prompted to do so after He noticed that two Leviathans were actually preparing to mate.
The Leviathans’ sex drives, however, were left somewhat intact. Seeing no reason to outright erase it entirely, the Creator instead NUMBED the serpents’ carnal hungers, neutralizing any sexual desires but not preventing them from occurring -- IF they were outside of Purgatory, where the numbing agent was active. Their sex drives would remain ‘inactive’ even outside of Purgatory, but could gradually reawaken after time spent around sexually-charged individuals and areas. (For example, the eldest Leviathan, Shadowborne, has a fully-reawakened sex drive due to how long he has spent on Earth, in the company of carnal pleasures and temptations.)
So while a Leviathan cannot procreate (at least not in any normal or natural capacity, and definitely not with each other -- the two hybrids, Ophiuchus and Kalanie are the only exceptions of Leviathan procreation, and neither of them are natural-born), their sex drives can be ‘reignited’ over time outside of Purgatory, and they can indulge as well as any other creature -- in fact, A HUNDRED TIMES BETTER, when at their finest.