 Like most of the other characters and species in the Halo universe , the Covenant were slowly developed during the initial concept phase and refined as Halo : Combat Evolved progressed . During the course of development of Halo , the designers decided upon three " schools " of architecture , for each of the races represented — the humans , the Covenant , and the Forerunners . For the Covenant , the team decided on " sleek and shiny " , with reflective surfaces , organic shapes , and use of purples . 
