Shadow: The Pendulum Trilogy Book 2 by Will Elliott
The second book in the Pendulum Trilogy, a visionary work of imaginative fantasy from one of genre fiction's most exciting new voices.
Eric and Case came to the world of Levaal through a door in an old railway arch, and it wasn't long before they found themselves caught up in the war to control this strange land. But the Wall at World's End, which once divided Levaal, has been brought down. Eric and his companions are forced to flee from the Tormentors, the dreadful creatures that poured through the breach, and there are rumours that one of the great dragons has escaped its sky prison.
But there is even more to fear, for the transformation into a god of Vous, Friend and Lord of the world, is almost complete, and a being called Shadow who looks remarkably like Eric is wandering Levaal with great power but no purpose it yet understands.
The end might be coming faster than anyone thinks.