Your Dexterity score increases by 1, and your Charisma score increases by 2.

Alu-fiends are immortal beings, and maintain the appearance of young- to mid-adulthood after reaching the age of about 25 years.

You have inherited the natural hardiness and resolve of your mortal parent, necessary in a world where danger lurks behind every corner, and particularly strong for your parent to have successfully mated with a succubus. Your Constitution score and either your Wisdowm or Intelligence score both increase by 1, and you have proficiency in one of the following skills: Survival, Medicine, Nature, Perception, Insight.

Once per long rest, you may cast the charm person spell. Charisma is your spellcasting ability for this trait.

You have two leathery wings which you can use to fly up to 1.5x your walking speed. You are not entirely proficient with your wings, however, and you tire easily. You may end up to 3 turns in flight, at which point you will fall to the ground (taking whatever damage is appropriate given the height of the fall) and be knocked prone. Your DM is also at discretion to describe some condition (such as a particular spell effect, amount of damage taken while flying, or other circumstance) that may lower your flight speed or cause you to fall while flying; you may also work with them to establish a point where you gain full mastery over your wings, if you wish.

Due to your demonic genes, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.

You have proficiency with the Persuasion skill.

Your mother, as a succubus, could change her appearance at will, and was a master of deception. You are far from her level, but with the help of a little makeup as a base you can channel a portion of that power. You know the first-level spell disguise self and you cast it as you would a cantrip, though casting it requires the added material components of a hand mirror and either a pad of foundation, a tube of lipstick, or a pencil of eyeliner. Note that you are not simply applying makeup; rather, the makeup acts as a catalyst or raw material that the magic of the spell acts on. You are also still able to change your appearance in any of the ways mentioned in the description of minor illusion; the makeup does is not a restriction of your physical changes. If you are in possession of a component pouch, you may presume that you have these materials on hand for as long as you have the pouch.

When channeling disguise self in this way, you have advantage on one deception, intimidation, or persuasion roll of your choice. You may only use this advantage once per casting, regardless of how many relevant checks you must make during the duration of the spell.

Upon reaching level 5, you have some sort of reconnection with your demonic lineage. It may be an encounter with one of your parents, a vision of your ancestral past, a discovery of a family heirloom or secret, or something else entirely. Whatever it may be, the event forges a deeper link with your succubus nature. You gain proficiency with longswords, rapiers, whips, and shortswords. You also gain resistance to fire damage, and with it a vulnerability to radiant damage.

[Note from your friendly neighborhood Crossark: You will have to note these changes manually when you hit the appropriate level. I can't work out how to set up modifiers like proficiencies and resistances so that they trigger at a certain point. My apologies.]

Your propensity towards sexual provocativeness is not just a matter of taste -- it is a direct inheritance from your succubus parent, and as such, you have become accustomed to wearing revealing garments. Due to this experience (and perhaps a bit of devilish protection at the hands of your mother), when you are wearing light armor you get the AC bonus of the corresponding set of medium armor (see list below). 

• Cloth armor types (Common/Fine/Traveler's Clothes; Costume) --> Hide armor (AC 12 + Dex modifier, max +2)
• Padded armor [Stealth disadvantage] -->  Scale Mail armor (AC 14 + Dex modifier, max +2) [Stealth disadvantage]
• Leather armor --> Breastplate armor (AC 14 + Dex modifier, max +2)
• Studded Leather armor --> Half Plate armor (AC 15 + Dex modifier, max +2) [Note: NO Stealth disadvantage; you are still wearing Studded Leather armor, after all]

You gain proficiency with the Chain Shirt armor type starting at level 3, but you equip it as a modified version called Chain Bikini or Chain Loincloth, depending on gender. It has an armor rating of AC 7 + Dex modifier, max +2, and can (and if you want to avoid pinching, probably should) be worn alongside light armor.

Starting at level 11, you gain a free feat called "Seriously?!". Even you have to admit that the extent to which your Succubus blood magically bolsters your natural toughness is a little absurd, but at least it significantly frees up your movement. You gain proficiency with all medium armor, but only in Bikini/Loincloth forms. When wearing Bikini/Loincloth armor without any accompanying light armor, it gives you the AC of the corresponding full set of medium armor plus your Dex Modifier (before class or other non-racial bonuses). If they are worn in tandem with light armor, they get half (rounded up) of their original AC plus your Dex modifier to a maximum of +2, as described in the Chain Bikini example above. These modified versions of the armor have the same disadvantages on stealth as their full-bodied counterparts.

[Note from your friendly neighborhood Crossark: You will have to note these changes manually when you hit the appropriate level. I can't work out how to set up modifiers like proficiencies and resistances so that they trigger at a certain point. My apologies.]