The Hunter Elites or H.E.'s were grown from the DNA of sangheili and altered into monsters.
They were first seen in the Battle of the human-controlled planet Kal-dera. There they killed all enemies and captured Ann. Then they attacked the sangheili homeworld. There they all but wiped out the sangheili. Then they were re-deployed for combat in space. They only went on missions that helped advance the Xenomorph race to complete conquest. Afterwards they became bodyguards for important generals and leaders of the Xenos.
The look like the halo wars version of an elite, but are as big as a hunter.