From Destinypedia, the Destiny wiki
The Monstrosity Ogre appears in the second encounter of Battleground: Foothold. When the hacking percentage reaches 75%, it will appear alongside a massive horde of Hive, including two Disruptor Wizards and a Wretched Knight. It tends to stay in the column room, but will bombard the players with its blasts and slam them if they dare to get too close. It is recommended to defeat it to make the fight easier. If it still lives after the hack is completed, it will disappear soon after.