Eos's words carried the power of his Will, and so it brought with it all the information the Beast would need to know about the sanctuary that Eos was offering.
It was a world built from the essence of his Origin Realms, which was hidden in its shadow. This was a space that only Eos knew of, and if it could hide here, no one would be able to find it until it revealed itself or the Origin Realms were destroyed.
The Beast knew that the Origin Realms would not be easily destroyed even if they were conquered, and so it was greatly assured of this realm's safety.
In addition to this, there were the words Eos had said about its interaction with End. Only a fool would not see that the Beast had lost most of its Dominion, and soon it would not be able to stand at all in the stage of Existence, and if it does not want to be devoured, it either serves a higher power, or becomes the Avatar of End.
