Agonizer 9000, Pain and Terror are a main story Bosses.
Pain and Terror are encountered after killing Agonizer 9000 during the story mission: "Blood Drive".
Pain and Terror don't respawn and have different Loot Pools!
Agonizer-1500, Backburner, Damned, Crader EM-P5, Loaded Dice
The Dictator, White Elephant