Barry knew, objectively, that there was no way he could survive. Once the demon inhabitants of the world realied that Dana was now the one in charge, and that he was Dana's enemy, they would find him and kill him. Defending himself in his pitiful human body was a joke of an idea.
But he might well die before that. His eons-old human body was sending him long-forgotten messages, of thirst, of hunger, of sweltering in the miserable heat and the harsh pressure of Astara's demon realm. The message which dominated all others was thirst. Most of the water sources of Astara's world were foul, but he seemed to remember a clear pool at some distance that Astara kept to occasionally look at her reflection. Very well, at least he might have a chance to die with his thirst quenched.
Before he could make it there, though, he felt a ripple in the fabric of reality. He couldn't say there was anything that identified it, exactly, but with a sinking heart he recognized it. Astara was dead, gone forever. All of his loyalty had been for naught. A tear rolled down Barry's cheek--the only tear in all the worlds of the multiverse, in all the hells, that would be shed for Astara.
Somehow he had made it to the pool, his only goal now sheer survival. He knelt, and greedily drank, ignoring the slight sulfurous taint. He raised his eyes, and for the first time since he had fled Dana, he felt a ray of hope, that maybe his life wasn't doomed to a quick ending.
A gate had opened--the ripple caused by Astara's death had disturbed some of the many spells she had placed on Barry's world, and in their dissolution they had revealed a gate. Barry didn't care what was on the other side, any fate was better than death at the hands of Dana's servants.
He plunged through.