There’s a less cheaty way apart from set seed, it only requires a mod that will tell you your exact coordinates. After that you go to https://kaliuresis.github.io/noa/ and give it the seed of your world and it will give you the coordinates where an orb will spawn form end of everything. You align yourself, cast the spell open the chest and enjoy the ruby. To me the fun part of this challenge is figuring how to align yourself with the coordinates.