Lucifon is the Prince of darkness. Olive meets him in the Western Desert. He led the army against the kingdom years ago, and retreated after his defeat at the hands of the hero.
In the Western Desert[]
If Olive camps in the place marked "Demon Abode", then upon waking she will meet Lucifon. He will offer her a drink. If her faith is 20 and up, she will automatically refuse it. He will then offer her some power "in deference to [her] spunk." If you accept his offer he will raise one of the following attributes of your choice:
The stat increase can be anywhere from 1-50 points. However, Olive will lose some faith in exchange (anywhere from 1-15 points). Her sin will also increase by 25 points.
Nothing will happen if you refuse his offer.
If Olive's faith is below 20, she'll automatically cave in and drink the liquor which will increase sin by around 80 points. This is quite useful if you are aiming for one of the dark endings (i.e. Princess of Darkness), plus it's a requirement to have him as Olive's lover.
Tips and Tricks[]
This is repeatable each and every time Olive steps into the Western Desert if she has enough Faith, and the stat gain from Lucifon in this manner for any stat is much, much more than any Class in the game can provide short of some S-level classes (i.e. S-Level Strategy or Science for Intelligence), making it highly valuable for the small amount of Faith lost --- especially if Olive managed to accumulate a sizable pool of it early on from Church work and Theology classes (either of which can easily regain the lost Faith points later if you want to have Olive avoid a dark ending). This is particularly useful for earning the required 800 points of Refinement for the Ruling Queen ending in a reasonable amount of time, and without needing to spend exorbitant amounts of gold (and time) on Protocol classes in order to raise it.
The Sin gain from trading with Lucifon is slightly more concerning, but can be easily offset by Church Donations to clear it out provided Olive also has more than enough Morality to prevent going delinquent. In fact, the location where Lucifon appears is also filled with Skeletons which give anywhere from 250 to almost 500 gold per kill --- making it an ideal place to grind for gold and easily make up for the gold lost to donations later.
Marriage Ending[]
It is possible to get a marriage ending involving Lucifon. If everything works out, one night he appears under Olive's window, tells her that he always knew she'd grow into a beautiful woman and gives her a love declaration. Olive is rather thrilled by the idea of marrying someone as rich and powerful as Lucifon, and to dissipate any doubts he points out that she cannot be happy either on Earth or Heaven any longer due to her Sin; this persuades her to run away with him and become his Dark Bride. She leaves without saying goodbye to her father or Cube, and is never seen again in the kingdom afterwards.
To get this, Olive must have 300+ Charisma, 200+ Refinement and Sin more than double her Morality. She must also have drunk Lucifon's liquor at least once.
It is considered to be an incredibly bad marriage, and the gods will blame your sins for having let that happen.
Tips and Tricks[]
This is surprisingly involved for an ending so bad. You need to reduce Olive's Faith to below 20 to make her accept Lucifon's drink. One convenient way is using his gifts a lot to get it low. Focus on raising her Charisma and Refinement after that, and keep raising Sin by killing monsters or accepting more drinks. If you want to avoid Sinful endings you could raise Morality to 30 and prevent Sin from reaching 500.