The trait Seven stars is a trait which limits the user to 7 skills but allows the user to quickly grow his skill proficiency and even evolve the skills.
The trait was named by Eres after seeing his peculiar characteristic. A characteristic that allowed him to catch up to Kangtae, Keldian, Eres and stand shoulder to shoulder with them despite starting 20 years late.
When Hansoo learns a skill, the trait allows him to receive the intentions and experiences of the create of the user of that skill and assimilate it. This lets Hansoo understand the skill better than anyone, increase the mastery of the skill quickly and become closer than anyone else to the one who has mastered it before.
The best part about the trait, Seven Stars, is not really that skills grew fast and beyond their limits. It was the fact that it gives the user the right to break through the ceiling that stopped everyone else. The true identity of the Seven Stars is as one of the many forms of the Transcendent Stars.
Even when walls existed, there are existences who could break through the ceiling and grow. Transcendents. People who had the rights to break through the limits set by the world and go above and beyond. This right was completely up to one's potential (such as a trait). People who weren't born with this couldn't even dream of such a thing.