Khans stand over 7 feet tall for the last 500 years. Before that they were smaller when turians but with their habitat driven away genetic mutation happened in one generation quickly giving power to small agile humanoid creatures. At that time they developed a secondary neural network which took the pain and absorbed converting it into rage which only helped them in battle rather when feeling it. They were completely painless. They also developed a strange eye-sight being able in fog better when in light. Their skin also hardened becoming more smoothier but the same time more hardened and fatter. Emotions became important part of their life being able to release greatest emotions without moving a limb, but this was a unique ability between them.