The Foe are the enemy alien race in Defender of the Future. They are in some ways almost similar to the Vortex race of the original Genesis games. They are an aggressive race that wishes to colonize and obliterate all planets that come in their path. Unlike the Vortex, they have a fleet of ships instead of just one mothership. In the intro it is stated that they "devour" civilizations and planets but it is not known if this means using them as food sources like the Vortex did. They even utilize kamikaze tactics as is shown with the ships that try to break through The Guardian's forcefield and are instantly destroyed. Eventually they destroy the upper half of the Guardian and begin to attack the ocean.
Outside of their ships, The Foe are not seen directly other than a cutscene where Ecco is said to take their form to attack their ship. The form Ecco takes is a flying dinosaur-like creature, resembling a Geiger-esque pterosaur-like beast with a wide triangular-shaped head.