Just a while ago, I was in the deepest part of Ryuudouden in the depths of the unexplored region, The Dragon’s Tomb.
It should be so far away that the linear distance is 10,000 kilometers. Assuming transfer magic was used, you’d have to do a long-distance transfer more than 10 times, it’ll be so impossible that even the Demon Lord who took pride in her absurd amount of magical power can’t do it in one go.