Kaos are circular rocks that have spikes protruding from their sides and have faces on the surface.
They are first seen in Ocean Palace in Sonic Heroes. When a team enters the area where there the Kao are found, they will begin rolling to chase the team and will try to roll over the team. Eventually, two more Kao will roll along with the first. The team must outrun the Kao in order to escape, continuing the first-level-run-from-the-danger theme.