From Halopedia, the Halo wiki
Bloodfuel Grunts are equipped with a form of backpack and with unidentified weaponry. These weapons are seemingly capable of "siphoning" the health out of the target of the weapon and healing the user wielding them. They are lead by Jiralhanae Bloodfuel.
The Bloodfuel Grunts are classed as core infantry, and performs well against infantry, vehicles and aircraft.
List of appearances