On paper, it would seem like a good idea to become the vassal of a Stellar Kingdom since that would give them a backer in the future. At the same time, this would also provide them a path to further their own cultivations.
With the resources that the Tai Stellar Kingdom had, it wouldn't be hard for them to help these True Soul Realm Experts break free of the shackles of the Soul Realm and reach the World Realm.
But that was only in theory.
The experts that were gathered here knew exactly what it meant to become a vassal of a Stellar Kingdom.
To put it simply, they would be taken in as slaves by the Stellar Kingdom.