In Infernax, there’s a hidden morality system. You can finish the game as good or evil, but if you really want to commit to one side or the other, you can actually earn ultimate good or ultimate evil ratings.
If you want to get ultimate good, you’ll need to find the Necronomicon and use it to banish Baphomet, all while keeping the highest possible morality rating. This is an incredibly long journey, so I’m going to lay out every step for you.

Guide credits go to Josh Wirtanen

In the very beginning of the game, you will encounter a man who is turning into a demon. You are given the choice to either kill him or try to help him. If you kill him at this point, you’ll block yourself from the later portion of this quest line. If you try to help him, though, he will turn into a monster called Paimon, which you must defeat in combat.

If you defeat Paimon, the man’s wife Lillian will see and run off. She has a house in the bottom level of Arkos, and if you visit her there (once you have access to Arkos), she will give you a quest to rid the world of Paimon once and for all.

Your next step is to travel to Kastki and visit Alan (who runs the Magic Shop there). He’ll give you an incantation. Now, travel back to the spot where you beat Paimon the first time. The corpse should still be there. Use the action button to say the incantation and trigger the second Paimon fight. Note that this one is way more difficult than the first one — this is definitely designed to be an endgame fight.

There’s a cathedral in Darsov. If you go inside, there’s a door that leads to the bedchambers. If you go through it, you’ll find a monk with a chest of money for the poor. He’ll ask you for 25 gold. Give it to him. (If you want to be evil, you can smash open the chest and steal all the money, but I’m pretty sure this does have an impact on the morality system.)

In the garrison in Darsov, you’ll find two more quests. In the first, a soldier asks you to clear away some bandits from the Valeshire Bridge. You’ll have to do this one at night, so go have a sleep in the inn if you need to change the time of day.

When you get to the bridge, you’ll have the option to either kill the bandit or spare him. You’ll want to kill him so work can begin to repair the bridge.

The second quest requires you to clear out an evil monster from a barn. The barn is just beyond the Valeshire Bridge, and if you can beat the Necro inside, the soldier will regain access to his barn. There is no option to spare the Necro; you’ll have to fight it.

Return to the garrison and turn in these quests once they’re completed.

There’s one more quest in Darsov that you can pick up early in the game. This one is from Genevieve, who lives in one of the houses in town. She asks you to cure her husband’s madness.

You can’t complete this until you’re pretty deep in the game, because it requires the Holy Light spell, which you’ll get from the Kadjanto Stronghold dungeon. Once you have that, you can mosey on over to the underground passage beneath Genevieve’s house. Inside a shack is Genevieve’s husband. Use Holy Light to cure him and he’ll give you a potion flask. When you’ve done that, return to Genevieve for your reward.

East of Combbelton Cemetery, you’ll find a camp of vagabonds led by a man named Robert. One man there will ask you to burn a holy tome in the cathedral in Darsov. Do not do this.

To the east of the camp is a house that belongs to a man named James. If you talk to him, he’ll ask you to clear out the vagabond camp. Return to the camp and ask the men to leave. Robert will ask you to drink with him, but don’t fall for his tricks; send the men scampering into the forest.

In the town of Arkos, in the shack pictured above, you’ll find a man who asks you to destroy the nearby dam. You can answer “Yes,” “No,” or “Never.” Pick “Never,” then fight off the onslaught of specters that appears.

Then, when you find the damn, don’t attack it (or it will flood Arkos).

In the garrison outside of Arkos, there are two soldiers with quests for you. The first one is to locate a man named Wilfred and give him a healing potion (an elixir works too). He’s just to the east of Arkos, past some waterwheels. Once you return to the garrison, Wilfred will tell you he was assigned to the watchtower. If you go just above Arkos, you’ll see that the watchtower is indeed unlocked, and you can go inside to see how this side story ends.

The second quest line is a bit more complicated. The soldier wants you to spy on some cultists, but in order to do so, you need to acquire the password to get into their hideout.

This requires you to go back to Darsov and locate Handsome Han. In case you’re not sure where to look, Han lives in this house:
When you get to his house, you’ll find that he’s being attacked by cultists. Kill the cultists and get him to spill the beans about the password.

Once you have the password, you’ll have to go back to Arkos, then find the cultist hideout above the town. It’s this building here:

If you go east of Arkos during the night, you’ll encounter a crowd of people who have caged a demon. You can either try to reason with it or kill it. If you reason with it, it will break out of its cage and kill some people in the crowd. If you burn it, it will just burn inside the cage until you put it out of its misery. You’ll definitely want to burn it here to save the townsfolk.

Once you get the Precision Strike skill (from the Combbelton Necropolis dungeon), you will be able to smash through cracked walls. Go to the location shown in the map above to find Danielle’s house, which you’ll need to smash a wall to access.

Once you’re in her house, Danielle will ask you to kill a monster in her basement, then open up the cellar door for you. Go through it to face Mammon.

Now, the trick to this boss fight is to deflect its fireballs back at whichever eye is open. You can do this by hitting each fireball with your mace (projectile deflection is a secondary benefit of Precision Strike). This can be a little finicky, but you just want to make sure you’re aiming at the open eye and not the closed one. If you’re feeling extra sassy, you can try to hit the smaller projectiles back at it too, but those are a bit harder to hit. The bigger fireballs are enough to take it down if you have the endurance for it.

Once Mammon is vanquished, return to Danielle to learn the Guided Strike skill

Once you get the Skycall skill, you will be able to travel back to the Shores of Upel (you can also get there using the Teleport spell). There’s a single house there, but the door is only open during the day. Inside, you’ll find an old hermit who asks you to burn down every town. Answer “Never,” and you’ll be teleported to a new area where you’ll fight the Faceless One.

In the village of Katski, there is a house on the bottom right-hand side of the town (to the right of the shrine). If you go inside during the day, you’ll find a man named Michael who is having some bad dreams. He’ll ask you to cleanse them.

First, you’ll need an elixir, which you can buy from Mary in Kadjanto Peak. Bring Michael an elixir to start the dream sequence. You’ll be teleported to the Dreamscape, which is a cakewalk compared to Stormheim Castle (which you should have cleared by this point), and you’ll have to beat Crocell. Once you do, you’ll be teleported back to Michael’s house. Talk to him so he can thank you and give you 300 gold.

Once you clear Stormheim Castle, you’ll find Julius to the west of Darsov, and he’ll tell you to come to the cathedral quickly. This triggers the exorcism quest.

To the east of Kastki you’ll find a house next to the garrison. Inside is Caroline, who asks you to deal with her skeleton problem. You’ll need to continue to travel east and perform some acrobatics to get to the right spot.

This one takes a little more effort to get to than Josephine’s skeleton, because you’ll need to solve a simple puzzle. There is a big gap in your way, and an unreachable lever to pull to get to it. If you use your Familiar spell, your bird will pull the lever for you, extending a bridge so you can get to the other side of the gap safely.

Once you’ve reached the other side, you’ll find a house. Go inside, then go into the basement to find a skeleton named Remus. Remus will ask you to spare him, but you’ll want to kill him instead (if you spare him, he will murder Caroline).

You will run into his friend Brutus way out by Kadjanto Stronghold. After beating him, break open the cage to free a wizard and get the Doves upgrade for your Familiar spell.

If you’ve done everything listed above, you should be able to pick up a quest from a soldier inside the garrison at Kastki. He’ll ask you to defend the town relic, so you’ll have to go to the Kastki mausoleum during the day. Inside, you’ll be attacked by cultists, and the mayor’s assistant will murder a priest. Kill the cultists afterward. Don’t worry; they’re not too difficult.

Once they’re defeated, return to the soldier in the garrison. He’ll suggest that you pay a visit to the mayor to get to the bottom of this. Go to the mayor’s house (which is just to the left of the gallows) to witness a horrible scene. The mayor will flee through a door (which was previously locked) and you’ll need to chase him. Once you confront him, a scene will play out that I won’t spoil for you.

Once you’ve completed the mausoleum quest line (above), the other soldier in the Kastki garrison will ask you to return to Tancred in Darsov to see if he can lend some support to the troops in Kastki. You’ll arrive in Darsov at the scene of a skirmish. Help Tancred defeat the cultists, then you’ll have to make a decision. Do you keep the troops in Darsov to bolster it against the impending attack, or do you send some of them to Kastki to defend that town against monsters?

If you send troops to Kastki you’ll have a lot less support in the upcoming battle. So if you think you can beat the cultists without a sizeable army, send them off to Kastki. Otherwise, bolster Darsov.

When the battle is over, Tancred will devise a plan to break into all three cultist hideouts and slaughter them, you’ll have to do them in this order:

1. Tohan Passage
   
2. Mount Kastka
   
3. Kadjanto Peak

When that’s done, you’ll finally be ready to confront Robert in his hideout. That hideout is way out by Combbelton Cemetery. Here’s where it is on your map:
When you confront Robert, he’ll send several waves of skeletons to attack you. If you can survive, a soldier will kill Robert.

Once Robert is dead, you can grab the Necronomicon off of the pedestal. You also now have access to the Hidden Crypt dungeon too (if you smash open the wall behind the Necronomicon’s pedestal).

Now that you have the Necronomicon, you are ready to confront Baphomet. You will, of course, need to clear the five main dungeons first. But when that’s done, return to Urzon Citadel.

In a playthrough without the Necronomicon, you would simply fight Belphegor and the game would end. With the Necronomicon, though, you open up the most brutal dungeon in the game. Complete the dungeon, kill Baphomet, and revel in the fact that you just completed an ultimate good playthrough!