From Soul World where Damien was originally situated, the Beast Domain was a considerable distance.
It was adjacent to Eden, however, actually reaching the Beast Domain took far more effort than just traveling through Eden.
After all, the border was filled with ferocious wild energy, a cosmic phenomenon that acted as a natural defense line on the border of the Beast Domain.
This defense line was the main reason the Nox hadn't immediately taken care of the Beast Domain's forces and instead chose to focus their efforts on Soul World after the destruction of Eden.
While it wouldn't have been too much of a problem for Damien to brute force his way through this defense with the Breath of Nothingness, he was currently prioritizing efficiency.
For others, making their way halfway around the universe to enter the Beast Domain was far too taxing, however, to Damien, it was light work.