The T'rran are the typical, average, nothing-extra-special Humons. They have no magical ability, have a low to moderate Potential Scores in Wisdom and Intelligence, but are skilled workers in whatever they apply themselves to. The T'rran were the held the longest as slaves before the Great Kaatyclyzym (GK) and its resulting Slave Revolts.
After the GK, the knowledge of slavery had been lost, but the ability to work remained innate, and thus the T'rrans built the first cities and accomplished the most for meeting the needs of others around them. After the chaos of the GK, the other races were grateful to the Humons and especially the T'rran for their willingness to work for the greater good, and they were rewarded for their labors with grand houses, wealth, and art as gifts, for providing the needs of the many.
However, the other side of the T'rran coin is that some are also lazy or self-serving. These, however, typically have ancestry in the Ensesine line of Humons. These might or might not be skilled workers, but they grumble over their work and are usually given less in gratitude gifts for their work.