From Halopedia, the Halo wiki

The venatores were a class of Warrior-Servant serving the Forerunner navy. Venatores served as experts in the art of stealth and decapitating strikes.[1] They operated war sphinxes and other specialist strikecraft for long-ranged strikes and close-ranged ambushes.[1] A venatore may also be responsible for directing their ship's millions of autonomous hunter-killers on long-range strikes.[2]

Sojourner-class dreadnoughts carried a contingent of five thousand venatores clad in war sphinxes.[2]