Nightmare Praetor

After coming to 4-5, you find the first boss, the Praetor, ready for a rematch against you. Be prepared for one hell of a fight.

The Praetor now has 45k health, beating even the Solemn One. Her and the simulacrums now deal 150 damage with Hellzone Flare, which poses far more of a threat late game, and she starts off with firing 3 at once, so you can easily take 450 damage from one attack. The Simulacrums still have 33% of her health, meaning that they have 15k health each, which is far harder to eliminate. Her passive of negating damage over 250 is now more noticeable late game, so you need to play it carefully. She still has phase changes at the same health points of 66% and 33%, but when they happen, large Aspects spawn instead, which are insanely threatening, but don't turn into smaller ones upon death, which is somewhat comforting. Her Devastation Beam can now track while firing, meaning even if you avoid it, she could move it over and still kill you. Be patient for this horrifying rematch, and with enough teamwork and strategy, you can eventually overcome this fight.

With her defeated, you have truly beaten Solemn Quest. (Until Nightmare Mode is extended to the other areas, that is ;)