The Universe is ever expanding so how does someone travel from one place to other places in the universe but most importantly return?
Traveling the space was adventurous and conquering the neighbouring life bearing planets was ever more rewarding. This led to a new galactic craving for conquest of untamed planets and its indigenous species by the leading recipients of all the conquests. The prominent victors of the conquests became the Supreme their followers became the Prime and their captives that later subordinated to a prime race became the subprime races.
While any race that has not achieved basic evolutionary/technological state necessary to promote space travel are lesser or unnamed race. Even if the planets inhabitants are intelligent and capable of communicating and or they possess advanced technology their race cannot become a genuine race of the universe if they cannot leave the confines of its own star system or have no connection to the ongoings of the Star scape.
The most concerning issue when galactic travel introduced by the followers of the Old Ones, the age-old ones and only creatures capable of inter galactic travel in the known Universe safely were that the challenge of instability caused by fluctuations in life and powerful beings remains, demonstrating the complexities of navigating and conquering the vastness of the universe. And if you travel long enough distance, you will lose your way. The sheer amount of time needed for the light travel makes the location of the destination to change because of the movements of celestial bodies. The distant world is observable through light that has been travelling through space for eons. By the time you observe it too much time has passed.
When two position origin and destination are taken for travel and used, it's impossible to reach the destination because the near instantaneous travel by folding space when compared to older light-based space travel because the relative position of destination measured through observation has already changed during the time taken for light from the celestial body is observed. A degree of change means your destination for space travel is lightyears away from the actual destination.
So, the Maler chart made by the Spirituals races leader and named in respect to his ancestor the child of a Titan and first spiritual. It shows the life that exist in the galaxy through the flow and tributaries of the Great Black River. And the Thorin race made the celestial chart that shows the changes in gravity. It depicts the expansion and contraction within the galaxy's large celestial bodies and its satellites. These two chats together formed the Star map which caused the start of expansion from the galactic centre to the fringes.
But still, these are only useful for individual or organisations but not useful for the entire race because the life fluctuation from a powerful being or a large group will lead to instability. Destroyed was the best outcome anything less the travellers would suffer terrible things like ending inside a rock or too close to a star and will be without any way to survive.
In sheer desperation nine of the 22 Prime races decided to use an entire continent from one of their planets for the biggest experiment the Large Body teleportation. Displacing a portion from their home planet with an equal portion from their prey, ingeniously creating a planetary predation where they would assimilate the part as quickly as possible while the teleported continent would contain a highly militarised army that would quickly conquer the land. And the continent itself will exert high control over the planet and without the support of the indigenous life form would corrupt the environment to that matching their home planet and created clone planets for the Prime races to expand into.