How to get this quest
After completing Path Towards Expertise, you can find the quest in the Adventurer's Guild.
Initial investigation
Talk to Julian then head out to the house guarded by a soldier. Talk to the characters there, examine the bookshelves, the small painting, the body, the bloodstains, and the burnt ground.
Once you interacted with everything, the quest's next objective will appear. You have to find a “key” and use Open Domain III on it (this spell is learned at the end of Reverse Summoning Ritual). The key is a black knight painting which can be found in 5 possible locations:
The six judgements
When arriving in the domain, Lucifer introduces the Justice mechanic. You start at 0 Justice, and have to pass 6 judgements before reaching Lucifer. For each judgement, you need to pull a lever or win a fight. This last option reduces your Justice by 1. If you choose to pull the lever, Charlotte will apply a modifier to your Willpower check (+/-30) on some choices. Here are the effects of the lever in each judgement:
| Judgement | Pull the lever up | Pull the lever down | Charlotte's influence |
| 1 |
+1 Justice +1 Corruption Charlotte's max HP reduced by 100 |
15 Vice required +2 Justice +1 Corruption |
Normal: helps you resist the Down choice In couple with Victor: nudges you towards the Down choice |
| 2 |
+1 Justice -2000 G |
5 Vice required +2 Justice +1 Corruption |
Normal: helps you resist the Down choice In couple with Victor: nudges you towards the Down choice |
| 3 |
+1 Justice All Aura's attributes reduced by 3 |
+2 Justice +1 Corruption |
Normal: helps you resist the Down choice In couple with Victor: nudges you towards the Down choice |
| 4 |
+1 Justice +2 Corruption |
+2 Justice +6 Corruption |
Normal: helps you resist the Down choice In couple with Victor: nudges you towards the Down choice |
| 5 |
+2 Justice +4 Corruption Hermann dies (blocking all further lewd content with him) If you know True Love's Blessing, you lose this passive skill |
+1 Justice +4 Corruption |
Normal: nothing In couple with Victor: nudges you towards the Down choice |
| 6 |
+1 Justice +2 Corruption Gabriel dies (you lose the opportunity to learn Light III) |
+2 Justice +2 Corruption Sophie dies (if not not already dead) Barry dies (otherwise) |
Nothing |
Fighting Lucifer
After facing the 6 judgements, you can face Lucifer. Your Justice score gets an influence on what happens.
Furthermore, if you fight Lucifer, Roland fights with him if he's still alive. Finally, they are joined by Lorraine if she was enslaved during Nothing But The Truth. If you fight Lorraine, you'll lose the opportunity to learn Pierce III.
Lucifer is a very tough enemy, even more so if he's backed by Roland and Lorraine. But you have Charlotte as a party member, meaning Aura will remove her collar if the party gets wiped out.
Lucifer can heal with both Desiderium and Boast: ATK. All of his damaging skills except Judgement of Pride are physical and do a lot of damage (flash bomb is thus essential to survive). To beat him without removing Aura's collar, it is advised to set up a combo to kill him quickly and avoid being having one of his hits connect, or to use Demonbane. Lucifer starts with 15000 HP and up to 900 DEF. If you want to kill him from full health with Rampage III, you will need in the worst case scenario to raise your ATK around 217 (possible with Overcharge and Heat Up) and use Lightning Sword II. Without Lightning Sword, you'll need around 265 in the worst case. In all cases, you also need to completely debuff Lucifer's DEF with Brittle and acid bomb to make a combo with Rampage work.
The day ends after facing Lucifer. All you have to do next is to report to the guild.