Monsters in the Mist — Mark Cheverton

Gameknight999 is hot on the trail of Entity303, who has kidnapped Weaver. He follows the mysterious villain into the strange mod world of Mystcraft, with green skies, trees with blue leaves, floating islands, and a blood-red moon.

Entity303 makes his way to a tower made of sparkling blue crystals, where he steals a linked book from the User-that-is-not-a-user, disappearing into one of Mystcraft's many ages.

Without the linked book, Gameknight has no way of ever leaving Mystcraft and returning to the Overworld. And besides, he can't leave with rescuing Weaver and sending him back to the past, which would repair Minecraft's timeline, making things right in the game once again.

The User-that-is-not-a-user has no choice but to visit each age, in hopes of finding the right one. But in the process he'll discover an unsettling truth about Entity303, and the deadly monsters the villain has left in wait for him.