It is part of the Forsaken - Tangled Shore Missions.
First, head into the cave and follow the waypoints until you have reached the mind-controlled Acolytes. In order to damage them, destroy the device and shoot them down. Be careful because more enemies will spawn afterward. Focus the Acolytes and then deal with the Knights. After that, scan the device in order to gain more intel about the boss and his whereabouts. While Ghost is scanning the object, you will have to defend your position and kill all incoming waves of enemies for a minute. This should not be hard.
When Ghost has finished scanning the object, you will get another waypoint. Follow it and you should encounter a Mindbent Ogre which you can take down easily if you are using special ammo or skills. After defeating him, jump your way up to the platform and defeat the enemies guarding the Amplifier that you need to disable. This process will take a while and you will have to defend Ghost while he is disabling it. Obliterate the enemies and follow the waypoints through the cave, until you have reached the Hall of Exalted where you should encounter another mindbending machine controlling enemies. Destroy it again and defeat the enemies.
Progress further and be careful at the Abomination that will pass through the portal. Follow the path behind and destroy the machines in order to start the fight with the Mindbender. He will be accompanied by many enemies so be careful. Also, do not use your supercharged on him if you have not yet chunked one-third of his health as he will teleport into another dimension. After he teleports, follow him through the portal and in order to damage him make sure to disable the shielding machines by shooting them. Make sure to keep distance from him and always have the higher ground as your visibility will be greatly reduced.
In order to complete the mission, defeat the Mindbender and escape the Ascendant Plane
|Forsaken||Last Call • High Plains Blues • Scorned • The Rider • The Trickster • The Mad Bomber • The Hangman • The Mindbender • The Rifleman • The Machinist • Nothing Left to Say|
|Shadowkeep||A Mysterious Disturbance • In Search of Answers • Ghosts of Our Past • The Scarlet Keep • In the Deep • The Nightmare Cometh • Beyond|
|Beyond Light||Darkness's Doorstep • The New Kell • Rising Resistance • A Link to the Future • The Warrior • The Technocrat • The Kell of Darkness|