Is there any explanation for the Conjunction of the Spheres?

Question

In the Witcher, the only thing we learn about the Conjunction of the Spheres is from the eponymous book found in both Witcher games:

"A cataclysm which occurred 1,500 years ago, trapping in our dimension many unnatural creatures, including ghouls, graveirs and vampires. These beasts have no ecological niches of their own and are merely relics of bygone times.

According to elven lore, humans arrived during the Conjunction, their own world having been destroyed. These human ancestors learned how to harness the power of primordial Chaos, and thus the first human wizards were born. Looking for a place in the world, humans took up arms against the Elder Races, who were unable to withstand the barbarians and ultimately surrendered. This is how humans came to rule the world."

a slightly different version can be found here:

"The cataclysm commonly known as the Conjunction of the Spheres happened one and a half millennia ago. A cosmic collision of several parallel universes ... ... The elves claim that humans also arrived in this world during the Conjunction. This occurred soon after they managed to destroy their own world."

1. What caused the cataclysm? It seems that the humans destroying their world might have something to do with it.
2. What is the relation of the Conjunction of the Spheres with primordial chaos, which "became more prominent in the world" post-Conjunction?

While this hasn't been revealed in-game, I was hoping that the novels may offer us some clues.

Answer 1

What caused the cataclysm?

The Conjunction of the Spheres was, most likely, a natural disaster, a cosmic collision of several parallel universes. There is no mention in the canon books, that it was caused intentionally by someone, and it is often referred to as 'cataclysm' which suggests natural origin. Fortunately for humans (their remnants from a world they destroyed), this caused their arrival to the world:

Elves claim that during the Conjunction, people migrated to this world. Shortly after they destroyed their home world.

-- The Swallow's Tower

What is the relation of the Conjunction of the Spheres with primordial chaos?

Chaos in the Witcher is a mystical, primordial power. There are two things often combined with this concept:

• For witchers, monsters they are fighting are manifestations of Chaos:

'Evil, I fought', repeated the witcher, 'was a manifestation of the activities of Chaos, activities designed to interfere Order'

-- Lady of the Lake

• For many of humans it was magic:

Magic is, therefore, the revenge and the weapon of Chaos. The fact that, following the Conjunction of the Spheres, people have learned to use magic, is the curse and undoing of this world. The undoing of mankind.

-- Blood of Elves

Both monsters and magic arrived after Conjunction of the Spheres. This is probably why it was said that after the cataclysm, Chaos "became more prominent in the world".

Answer 2

I may be wrong because I played Wild Hunt a couple of years ago, but it was my understanding the conjunction was caused by the elves under Eredin as they sought to jump across the worlds in order to conquer them, harvest their resources, and also because their abuse of magic while doing so led to the early decay of their native world, meaning, the White Frost.