To develop a distinctive look for the various species of the Covenant, Bungie artists drew inspiration from reptilian, ursine, and avian characteristics. A Covenant design scheme employing various shades of purple and reflective surfaces was used to visually distinguish alien from human architecture. The Covenant were generally well received by game critics, who appreciated the challenge they provided to players and often compared them to the series' other primary antagonist, the Flood. Several critics lamented the change of the main Covenant enemies from Elites to Brutes in "Halo 3" and conversely praised their return in "".