Zatiel could only sigh after hearing the World Tree's words. He was now sure that The Sage, or more precisely, the King in Yellow, was still alive.
Someone with the power to threaten an existence at the World Tree's level would not die so easily.
By using the entity in the Final Purgatory's first layer, he may have wounded the King in Yellow severely and erased many of his clones and avatars from the timeline, but that was all.
Another thing that Zatiel was sure of was that the King in Yellow's true body was not in the Prima Universe, or else he would have appeared the moment the Neo-Demon captured the avatar and stopped its self-destruction.
A Middle World's Crystal Wall would not have stopped the King in Yellow. In the worst case, he would have destroyed the entire world to take care of Zatiel.