Hey Guys. So I am creating a Tiefling Warlock character whose patron is the Fiend. His name is Ozai Hakulon. However, I am having a hard time coming up with a Patron for him that can be evil while Ozai is somewhat good. Do you guys have any ideas? It's not for a campaign. I just create characters for fun. He's a Tiefling with a subrace of a descendant of Mephistopheles.

Check out Bael - general in the armies of hell

Bael prefers to make servants out of his adversaries, and mortals bound to his service earn their wretched place by falling victim to Bael’s superior stratagems. Bael gladly spares the lives of those he defeats, but only if they pledge their souls and service to him. Although he is willing to corrupt almost any being in this way, he always destroys any demons he defeats.

Bael also welcomes mortals into his service if they can provide him with an advantage in his own politicking. He recruits savvy individuals and relies on them to represent his interests at Mammon’s court, which leaves Bael free to pursue his battle lust.

Hmm. Bael actually sounds like a good choice. So how about this. Ozai grew up in the city of Regalo as the son of an innkeeper who also a Tiefling. His father, Novak, was regarded as being a just and fair man who was usually called on to settle disputes, the townsfolk knowing his decision would be just. Growing up in the inn, Ozai learned to hold his own against bully guests and learned a little magic from mages who stayed a the inn. His personality is blunt to people he has no care for but can be manipulative when need be. When he was 20, he found a book left by a mage who had stayed the night before. Looking through the book, Ozai realized it contained a spell that would allow him to travel to the Nine Hells. Longing for adventure and to leave the inn, Ozai decided to use the spell. Knowing that it would be foolish to go into the Nine Hells unprepared, he bought several healing potions and invisibility potions from the local apothecary. Finally, when he was ready, he used the spell and stepped into the portal. When he looked around, he saw Bael, whom he knew as the Bronze General. He also saw Hutijin, Mephistopheles' second in command. Bael and Hutijin were dueling each other with neither one seeming to get the upper hand. Ozai watched the battle, quickly realizing that Bael was the better warrior. Finally, after two hours of constant fighting, Hutijin used a dirty trick and knocked Bael to his feet. Realizing that Bael would die, in an uncharacteristic moment of mercy, Ozai threw a healing potion and an invisibility potion at Bael, making Hutijin miss the fatal attack. Bael, now restored and invisible, began lashing out at Hutijin, who had no idea what to do. Fearing he would die, Hutijin flew away. Bael used his magic to pull Ozai from his hiding spot and, instead of killing him, thanked him for his aid. In return for Ozai saving his life, Bael agreed to be his patron, giving him immense power. However, Ozai would have to swear to seek out and destroy cultists of other devils, especially Hutijin and Mephistopheles. Ozai agreed, and Bael teleported him back to the inn. To this day, Ozai seeks out the other cults while also seeking arcane knowledge to further his patron's goals.

Also he would call upon Ozai whenever he needed to be represented in Mammon's court.

Any other ideas from you guys are still appreciated.

Quote from AkanosNovak >>

Any other ideas from you guys are still appreciated.

 Technically, Hutijin is more powerful than Bael, at least statistic-wise. Thematically it would make more sense for Bael to be fighting demons, instead of other devils. Also, Hutijin has truesight, which means he can see through invisibility. Oh, and both Bael and Hutijin automatically regain more hit points each round then is restored by a common healing potion.

Ahh. I see. Thanks for the info. I’m still new to D&D, having never played but wish I could. I’ll alter Ozai’s story to be cannon. 

But what did you think of they rest of story?

Quote from AkanosNovak >>

But what did you think of they rest of story?

 The rest looks pretty cool!

Thanks. So how about it is the same up to Ozai stepping through the portal. He steps through the portal and sees Bael fighting a horde of gnolls. Somehow they got into the Nine Hells. Although Bael defeats each one easily, there are too many and he is alone. Ozai uses the little magic he has to confuse the gnolls. With the gnolls confused, Bael slaughters them all. After defeating the gnolls, Bael finds Ozai, blab blab blab, becomes his patron, blab blab blab, Ozai has to hunt demon cults. 

Quote from AkanosNovak >>

Thanks. So how about it is the same up to Ozai stepping through the portal. He steps through the portal and sees Bael fighting a horde of gnolls. Somehow they got into the Nine Hells. Although Bael defeats each one easily, there are too many and he is alone. Ozai uses the little magic he has to confuse the gnolls. With the gnolls confused, Bael slaughters them all. After defeating the gnolls, Bael finds Ozai, blab blab blab, becomes his patron, blab blab blab, Ozai has to hunt demon cults. 

 Yeah, that sounds great! Canonically, the demons are at war with devils, and they have been fighting each other for centuries in an enormous war called the Blood War. Most of the fighting takes place on Avernus (the first layer of the Nine Hells).

Great. Now I just have to find a game to play him. 

Will Ozai quote Ozai from Avatar: the Last Airbender? Is he a firebender too? 

Yeah. I stole the name from the Last Airbender. 

Make sense for a Fiend Warlock. 

Quote from Vince_Snetterton >>

I have played a Hexblade with a backstory that was geared to my Hexblade being antagonistic towards his Patron.

You can certainly appropriate it and easily alter it for a Fiend. Now, mine was 3 pages long, so will do an altered TL/DR version here for a Fiend:

Tiefling's mom was a powerful wizard who was involved magical weapon-smithing for Realm X. While she knew it was extremely dangerous, she also knew the potential payoff of infusing Lower Planes magic into weapons had huge potential. During one of her experiments, something went wrong. She summoned Entity Y from the Nine Hells (Devil works better for the backstory). Tiefling entered the room just in time to witness his mother killed by Entity Y and, and recognized that Entity Y was about to take Tiefling's mom's soul back to the Nine Hells. Tiefling tried to intervene, futilely. Entity Y almost killed Tiefling, but then stopped. 

Entity Y then told Tiefling that Entity Y would release Tiefling's mom's soul, if Tiefling entered into a Pact to perform "various services in the future on this Plane" for Entity Y. Tiefling reluctantly agreed, and felt searing pain as he was branded on his chest with a small mark of that particular Entity. Tiefling watched as his mother's soul was released.

You now have as many plot hooks you like as time to time Entity Y sends word to the  player that Entity Y wants task Z performed. The reasons do or do not have to be known by the player.

 That's a pretty cool story. I might do that but replace the mom with his father Novak.

You could also go the Ghost Rider approach to your Feind Patron, namely "i get my power from harvesting the souls of the wicked and evil. In exchange for some of that power, will you hunt down and kill the wicked and evil for me so I get their souls?"

Then you can absolutely have a good character with an evil boss. It also gives you plenty of leeway to still be heroic even. Save a bus-full of children? "Excellent!" your evil patron says, "now they have more time in the mortal realm to tarnish their good and innocent souls, and some may eventually make it to my realm!" By all means, protect the good and innocent, longer life means more chances to turn evil!