It would probably take some time for the people of Helcrown and the elves to become acquainted with each other, but the process should not be too difficult. The elves had a high affinity for foreign races, and the people of Helcrown, who were willing to follow Y'zaks to this world were all diehard followers. They were steadfast in their pursuit of the "Great Unification". They embraced a multi-racial society without any criticisms.
There was another important reason: those who had the same misfortune sympathized with each other. Both parties had to flee their own country. When they met, the elves and the demons looked at each other with tears in their eyes...