User blog comment:GrandMethuselah67/World-1: The Neo-Methuselahverse/@comment-4867780-20190618141855/@comment-26322734-20190624145427

"Considering the titanic power of each and every Jotar, the sheer magnitude of the destruction they cause every time, and their relentless appearence throughout the Sol Federation, how long does mankind have left ?"

About 20 years if the Jotnar keep attacking at the rate they are.

"The remaining population is already less that half it was before the Corruption, while Jotun activity seems to have all but multiplied. At this rate, the Federation will probably be collapsing in just a decade, and humanity all but extinct by the next."

Oh yeah, things aren't looking good. That being said, the Jotnar don't really attack at the same rate all the time. For example, there were more attacks in the mid-nineties and early 2000s than now. This is because the Jotnar are actually created by humanity's innate psychic potential, basically the same as Freud's idea that life tends towards self-destruction. So there are extensive efforts from those in the know about this (mostly Black Spiral) and attempts to control humanity's psychological state through various feats of media and political manipulation. This had come with varying levels of success.

"Finally, if Jotuns are the psycho-reactive product of mankind's darkest emotions, why do their cores contain dimensional portals leading to other universes ?"

Think of it as an adaptation, except instead of it being in response to something, it's a product of mankind's desires. So say mankind's subconscious desire is "I want to die" (notice how Jotnar came during the Dark Age), reality filled in the blanks and created a creature that is nigh-indestructable. Reality is legitimately so broken because of the events that happened at the beginning of the setting that humanity's collective subconscious desire was able to warp the fabric of reality, creating creatures that were essentially sentient dimensional portals.

​​​​​​"Unless these portals represent mankind's greatest and most universal fear - the fear of the unknown - which would then explain why all Jotuns have that in common."

That explanation also works. Remember - the Jotuns represent humanity's tendency towards self-destruction and humanity's fears. Their creation wasn't a deliberate effort by humanity, but rather them subconsciously projecting a strong enough desire into the Psychosphere that it became "real" and reality filling in the blanks.