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

Concubi mature at the same rate as humans but can live centuries longer. Additionally, after they mature their appearance or physical body does not age past their prime.

Concubi are often evil, but can vary greatly depending on their particular lifestyle or personality.

Concubi are about the same size and build as humans, but are very toned and slender. Your size is Medium.

Your base walking speed is 30 ft.  If in your true form, you also have a flying speed of 30 ft.

Thanks to your fiendish heritage, 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 are considered to be both Fiend and Humanoid, and you are considered to have the "Shapechanger" tag. Additionally, you are resistant to fire damage and vulnerable to radiant damage.

As an action, you can change your appearance and your voice to that of a humanoid or fiend. You determine the specifics of the changes, including your coloration, hair length, and sex. You can also adjust your height and weight, but not so much that your size changes. You can make yourself appear as a member of another race, though none of your game statistics change. You can’t duplicate the appearance of a creature you’ve never seen, and you must adopt a form that has the same basic arrangement of limbs that you have. Your clothing and equipment aren’t changed by this trait.

You stay in the new form until you use an action to change into a new form, revert to your true form, or until you die.

As you subsist on sexual energy and desire, you do not need to eat normal food.  Your body can ingest and process normal food to help maintain the illusion of your form, but it does not sustain you.  As such, you are immune to tainted food problems, such as disease and poison.

Just like most other creatures, you have to eat something sustaining in order to maintain your body, in this case, sensual and sexual energy.  As a fiend, you can go just a little bit longer than normal humanoids before you start having side effects of hunger, being a week.  In those 7 days, your body still performs as if nothing is wrong.  After the 7th day without you feeding on a decent amount of energy, every day that passes grants you 1 more level of exhaustion, until the 13th day, in which you die.  These levels of exhaustion do not go away with long rests, but with feedings.

If you feed on sensual energy (5 minutes minimum of interaction, anything up to, but not including, sex), your partner suffers disadvantage on all Charisma, Intelligence, and Wisdom checks for the next 2 hours and looses 5 points of HP, you subtract 1 day from your hunger counter, and, if you have levels of exhaustion, you subtract 1 level of exhaustion from your total amount.

If you feed on sexual energy (1 hour minimum of interaction), your partner suffers 1 level of exhaustion until their next long rest after 24 hours have passed and looses a quarter of their HP, you subtract 7 days from your hunger counter, and, if you have levels of exhaustion, you subtract 3 levels of exhaustion from your total amount.  Removing levels of exhaustion can only be done once a day and unless your partner or someone else gets suspicious, your partner's lost HP goes unnoticed or attributed to something else.

If you have more than 3 levels of exhaustion and a single partner to feed off of, your mind is so devoted to your hunger that you run a high risk of feeding off their energy until they die.  After a sensual encounter, your partner must succeed a DC 5 + your exhaustion level Constitution check with advantage or have all their HP stolen, taking them down to saving throws.  After a sexual encounter, your partner must succeed a DC 10 + your exhaustion level Constitution check with advantage or suffer the same fate.

If you have multiple partners, they do not run any risk of dying, no matter how exhausted you are, each partner still suffers the listed side effect from the type of encounter, and you loose hunger equal to the encounter and number of partners.  Your exhaustion still only goes down once, as if you only had one partner.

As a concubi, you have a natural ability with charming people. You can cast charming spells with no material components and simplified verbal and somatic components.  In addition, any ability the target has to detect the charm effect, upon a successful saving throw or at the charm's end, is eliminated. This ability can be used a number of times equal to twice your proficiency bonus and all expended uses are regained after finishing a long rest.

If you have successfully charmed a target, while it remains charmed by you, you can kiss the target as an action once, causing the target to roll a DC 13 + you proficiency modifier Wisdom saving throw.  On a fail, your kiss causes the target to remain charmed for up to 1 full day from the time you kissed it.  If the target succeeds, you can not try the Alluring Kiss again on them for the next 24 hours.  After the spell that charmed it originally ends, the target obeys any verbal command you give it while still acting as normal as it can, as long as it does not suffer any direct harm or receive any suicidal commands.  If it does, the target can repeat the saving throw to end the charm upon it.  If the target successfully saves against the effect, or if the effect on it ends, the target is immune to any charm ability or spell cast by you for the next 48 hours.  This ability can be used up to your proficiency modifier and all expended uses are regained after a long rest.

A creature of deceptive words, Concubi have proficiency with Persuasion and Deception.

You can speak, read, and write Common, Abyssal, and Infernal.

At 6th level, as an action, your powers have grown strong enough to forge a telepathic link with one creature you have successfully Charmed, making it your thrall until the spell or ability creating the charmed condition ends.  You can control everything your target can perceive through the link from you, but your target has no control over what you can perceive from it.  This link extends out to 1 mile and allows you and your thrall to exchange thoughts.

At 10th level, your powers have grown stronger, allowing the link to extend out to 5 miles and the sharing of auditory senses between you and your thrall.

At 14th level, your powers are stronger still, allowing the link to extend out to 10 miles, you to forge a telepathic link with a second creature you have successfully charmed, and the sharing of visual senses between you and your thrall.

At 20th level, your enthralling powers are as strong as they can be.  The link between you and your thrall now extends to the entirety of the plane you are on.  You can now forge a telepathic link with a third creature you have successfully charmed, and you can cast detect thoughts, suggestion, or dominate person on your thrall any distance, up to your proficiency bonus number of times, with disadvantage on the Wisdom saving throw.  The thrall succeeding on the spell saving throw does not end the charmed condition, the spell just doesn't work.

As soon as the spell or ability charming a particular thrall ends, it leaves your thrall.  That creature remembers everything up to the point of you charming it and everything it physically did while under your enchantment, but does not remember any conversation or any information shared either way across the telepathic link during that same time, unless it succeeds a DC 10 Intelligence check before 10th level, a DC 14 Intelligence check before 14th level, or a DC 19 Intelligence check before 20th level.