From Halopedia, the Halo wiki
Mgalekgolo Captains are Mgalekgolo "officers" deployed by "Colony" to locations which require more direct involvement and supervision. Captains make sure Lekgolo colonies and gestalts operate at full efficiency during battles. Each Captain is linked directly to "Colony" and its distant bond-brother over a specially modified battlenet relay, often going into battle without its bond-brother. Unlike other Mgalekgolo, Captains are equipped with energy shielding.
Halo Wars 2
The Mgalekgolo Captain is exclusive to "Colony" and can be built at the War Council. Like other hero units the player is limited to one on the field at a time. They have immense durability at the cost of mobility, making them one of the slowest units in the game. Captains feature the Siphon ability to steal health from enemies and are able to agro enemies away from allied units. In Blitz Hunter Captains cost 260 energy and feature the Shock ability to decrease enemy armor, in addition to its normal energy shielding, passive Siphon ability, and Taunt ability.
The Captain is a unit available for play in the Blitz and Blitz Firefight modes of Halo Wars 2. It is available to players playing as Colony. The Hunter Captain Blitz card has the following attributes;
The Hunter Captain is classed as a hero infantry, and performs well against infantry, vehicles and aircraft.
List of appearances