There are two books titled Between Worlds in The Witcher 3: Wild Hunt. One is added by the Hearts of Stone expansion, and the other by the Blood and Wine expansion.

Olgierd's copy Edit

This book describes the beings inhabiting the Outer Spheres. Geralt reads the tome to best understand what Olgierd von Everec was doing in his study, during Hearts of Stone expansion.

Associated quest Edit

Journal entry Edit

Of all the beings inhabiting the Outer Spheres, the spirits of the elementals are the most foreign to human nature. They possess a will of their own and are intelligent, though not in the way of men. For there is no way to fathom their drives and intentions.
Genies, the most powerful of the elemental spirits, prove the most difficult for men to commune with. Only the true masters of magic have perfected this art, which demands long years of study and risky experiments. Yet even the most adept at the magic arts cannot tame a genie, merely force it to perform certain acts against its own volition.
They say the mage Stammelford once commanded a d'ao to move a mountain blocking the view from his tower, but even he could never convince a genie to be a willing helpmate in his work or to give sound advice, for the reasoning of these creatures is beyond human understanding.

Castel Ravello herbalist's copy Edit

When Geralt explores the herbalist's back store at Castel Ravello Estate he can discover a different copy of Between Worlds, during the Blood and Wine expansion.

Journal entry Edit

In a plane not unlike our own there once lived a ruler named Azgaryk. When he was an old man, he fell ill. He felt that he would soon die, so he summoned an evil spirit – Marbas – and made a deal with him. Azgaryk would live until his son came of age and ascended to the throne.
10 years passed. Azgaryk died, and next to his body Marbas appeared and turned to the heir to the throne:
"Your father promised me something. Now you must pay his debt."
"And just what did my father receive from you in return?" asked the heir. "And what do I owe?"
"Your life," said Marbas, and cut the heir's throat with his claw. The boy had not yet died when Marbas opened a gate to another plane. Out of it came a mercenary army, with the evil spirit Berith marching at its head.
"Marbas sat on Azgaryk's throne. Ill times had come to the land. The people rebelled against the demon's rule. Marbas sent Berith and his army after them. Berith slaughtered all the rebels. His armor glistened with blood. People began to call Berith the Crimson Sovereign. Marbas' appetite was not sated, so he sent the Crimson Sovereign to conquer neighboring countries. And so it went on, for hundreds of years the Sovereign continued his march, losing soldiers as he went. But Marbas was never sated."
Finally, there came a time when the people of all the continents were united under Marbas' rule, and the Crimson Sovereign was left alone, without an army. He knelt before Marbas and said:
"You hired me and I have carried out my task. You promised me a weapon from which no shield can provide protection."
"You shall receive it," Marbas said, flashing his teeth. He reached into his garment and drew out a vial filled with plague bile.
He flung it at the Crimson Sovereign. Yet the Sovereign knew Marbas well enough to expect treachery. He opened a passage to another world and fled before the vial full of plague could hit the floor. Yet ill luck would have it that while he was fleeing, a gale came flying out of his open portal. It opened the window to Marbas' throne room and spread the plague bile out over the entire world.
Ever since Marbas has dwelled in a tower standing above a continent of dead bodies and beasts transformed by the plague. And Berith, still calling himself the Crimson Sovereign, wanders from world to world as a mercenary. Searching for vengeance.