

They lack durability, but use powerful laser beam weapons and are immune to infection by the Flood. Sentinels are able to hover around in enclosed spaces and produce an energy shield when under attack. Other enemies include Sentinels, aerial robots designed by an extinct race called the Forerunners to protect their structures and prevent Flood outbreaks. A secondary enemy is the Flood, a parasitic alien life form that appears in several variants. Their forces include Elites, fierce warriors protected by recharging energy shields similar to the player's own Grunts, which are short, cowardly creatures who are usually led by Elites in battle, and often flee in terror instead of fighting in the absence of a leading Elite Jackals, originally space pirates, who wear a highly durable energy shield on one arm and a form of handgun on the other and Hunters, large, powerful creatures composed of small worm-like colonies with thick armor plates that cover the majority of their bodies and a large assault cannon that fires explosive rounds of green plasma. The game's main enemy force is the Covenant, a group of alien species allied by belief in a common religion.
