You have no mouth, instead you have a long straw-like body part that you use to drink nectar or other liquids called a proboscis

As such, you cannot speak any languages, although you can still understand them and write just fine.

You also don’t have a nose. No one quite nose how a Butterfey breaths, but speculations are that they breath much like a butterfly, through a series of tiny openings along the sides of your body, called "spiracles."

Because of this little fact, most Butterfey don’t wear any clothing and armor, unless the clothing or armor breathes, is magical, or is Butterfeyan

You are limited in what you can eat, the only thing you can consume is liquids, including nectar, blood, potions, and soups with no solids whatsoever. Even a small piece of food could damage the inside of your proboscis and kill you.

Butterfey are extremely trusting of other races and they typically choose to see the best in people.

You can communicate telepathically with any other creature, regardless of what languages they speak,  by touching your antennae to their head. Most Butterfey attempt to ask permission before they do so

Your antennae also function as ears

You can communicate telepathically with any Butterfey as long as they are within 2000 feet.of you

If you are in extreme danger and are in need of help, you can call any Butterfey in the area and they will rush to help you out if they can and are willing.

Any butterfly in the area will also come and help as well but all they will be able to do is blind the enemy, and poison if they are able, this feature can only be used once a day

Butterfey are extremely perceptive creatures, the only problem is that they have no easy way to communicate what they see.

You have 12,000 little black eyes in two clusters, much like a butterfly, and through them you can see through any invisibility spells, whether it’s on a creature or an object, you can see right through them. it is as if you have a permanent See Invisibility spell on you

Magically hidden inscriptions on maps and other objects are not hidden either.

You can also see creatures if they are hiding behind 1/2 or 3/4 cover, no need for a perception check.

Hidden traps are not hidden from you

You cannot be surprised.

You have proficiency in perception

You are naturally adept at magic. As long as the spell requires material or somatic components, you can ignore the verbal components.

You have wings of course, and you have a flight speed of 60ft and a walking speed of 30

As long as you are conscience, you can ignore any and all fall damage.

You cannot fly if your wings are wet.

You have disadvantage on stealth checks while you are flying

Due to your lack of mouth and your many unblinking eyes, most view your presence as a bit unnerving. As such you have proficiency in intimidation

7 to 9 ft tall, your antennae and wings add an extra foot, so in reality you are 6 to 8 ft tall with an additional foot from the wings and antennae.

Your size is medium

80 to 100 pounds

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.

Your Strength score goes up by 2
Your Wisdom score goes up by 2
Your Constitution score goes down by 1

You have advantage on saving throws against being charmed, and magic can’t put you to sleep.

Just like Elves, Butterfey don’t need to sleep. Instead, they meditate deeply, remaining semiconscious, for 4 hours a day. (The Common word for such meditation is “trance.”) While meditating, you can dream after a fashion; such dreams are actually mental exercises that have become reflexive through years of practice. After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.

You understand, read, and write Common, Elvish, and Sylvian.

You may be fey, but butterflies don't live very long. You are on the younger side for a fey

Butterfey live to be 200 years old and they become an adult by the age of 20. They are Caterfey, which is the equivalent of caterpillar to a butterfly, for the first 10 years of their life and are in a chrystalis for 6 months before they become a Butterfey.

You are basically useless during your Caterfey form and when you are in your chrystalis you are extremely vulnerable and will die if your chrystalis is broken.

Caterfey never leave the fey realm or the safety of the hive. Only once they become a Butterfey do they leave the hive, or they stay to take care of the young Caterfey and protect the chrystalises, as they are a valuable bounty for treasure hunters, being made of crystals harder than adamantine and are immune to all non-magical damage and are vulnerable to all magical damage, they only have 1 HP, so they must be taken care of with great care.

Often Butterfey will keep the chrystals from their old chrystalises as jewelry or home decor. If they don't, it is used to spruce up and light up the hive. It can also be made into magic items or armor. 
All Butterfey weapons, armor, shields, and any other item made from Chrystals are called Chrystal items.

Even though these creatures have tons of strength, counting as one size larger when determining their carrying capacity and the weight they can push, drag, or lift, they have learned to be exceptionally gentle, so they can easily handle the chrystalises without accidently dealing damage.

You have two sets of arms, all four arms are useful for anything you do with arms. As your race naturally has two sets of arms and are born with two sets of arms and have always from the beginning has had two sets of arms, you know how to use them well and can do many things someone with only one set of arms can’t as you do have two sets of arms. At the end of the arms are hands.

If your class can only use one handed weapons, you can use two handed weapons.
If your class can use two-handed weapons, you can use three and four handed Butterfae weapons.
Even if your class can’t dual wield, you can.
If your class can dual wield, you can triple or even quadruple wield.

For example

You can dual wield two handed weapons,
quad-wield one-handed weapons,
triple-wield three one-handed weapons and a shield,
dual wield a two-handed weapon and a one-handed weapon while still using a shield,
dual-wield two one-handed weapons and a Chrystal shield.
If you are using weapons like this, you have double the attacks and can attack two different creatures at once as you have two sets of arms that do not get entangled easily because you were born with them and you know how to use them, the 12,000 eyes help as well

As Butterfey have the extra sets of arms, they have made weapons that only they can use.

You can wield a three-handed weapon and a shield,
wield a four-handed weapon,
wield a two-handed weapon and a Chrystal Shield.
If you are using weapons like this, you don't gain the benefits of double the attacks or attacking two different creatures at once.

Ranged Weapons
a mounted crossbow would be considered a four-handed weapon for you, as would a small cannon
You can shoot off 3 arrows an attack because you have two extra arms free to load the ammunition of any two-handed ranged weapon.

You can also use weapons sized for Giants. You must use two hands for a one-handed Giant sized weapons and all four hands for a two-handed Giant sized weapon.

You are also a natural grappler and gain all the benefits of the Grappler feat
You have advantage on Attack rolls against a creature you are Grappling.
You can use your action to try to pin a creature Grappled by you. To do so, make another grapple check. If you succeed, you and the creature are both Restrained until the grapple ends.