Psi-Line Humans are those that have undergone extensive modification through genetic engineering or are the children of thusly-engineered individuals. The end result of the genetic engineering is that the Psi-line humans have developed psionic powers to some extent. The range of their powers varies greatly from one individual to the next, but none of them has anything less than minor psionic aptitude.
The genetic modifications these individuals or their parents have undergone have almost all centered around the mind and other neurological systems of the body. While they may have also had physical changes made to alter their appearance, the majority of their differences are internal, having to do with organ structures and brain composition. However, they tend to be much less physically impressive than normal humans due to the amount of modifications that have been made in order to strengthen their mental prowess.