The Dream Sanctum: Through The Golden Door - The Dream Sanctum, #1

The most thrilling adventure begins when you close your eyes. Kai is determined to master the art of lucid dreaming, but he gets more than he bargains for when he accidentally tumbles into an entire world only accessible by sleep. One fateful trip through a golden doorway leads him to the Dream Sanctum, a place where people from across the globe share a lucid dream created by ancient and mysterious beings. Inside the Sanctum Kai meets Kwin, a brilliant and somewhat intimidating child prodigy, and Alastor, a skilled swordsman with unique powers and an even more unusual companion.
Alongside his best friend Lindsay, and occasionally an overconfident yet golden-hearted hero named Hercules, they set out on a journey to uncover and explore the dream world's wonders. But as a menacing red-eyed wolf appears and shadows begin to haunt the darkness, Kai realizes the Sanctum is in peril. When the Nightmares finally emerge, they engulf cities and devour dreamers, leaving them unable to wake up.
Determined to protect the world he's come to love, Kai and his friends wage a desperate battle against the encroaching shadows. Amidst this chaos, he begins to learn more about his mysterious new friend Kwin... as well as the dangerous secrets she's been keeping.