Threshers

Threshers are a race of intelligent, four-armed humanoids born from the survivors of the reaping plague several hundred years ago. Despite being such a young race, they have constructed a remarkably orderly, efficient society that actively seeks to trade and cooperate with many other communities. They live in highly-structured city-states colloquially called White Cities by other races, all of which are part of their nation-equivalent, the Godhurst Colonies, helmed in the Whitemark Islands to the far west of Feraweth.

Physiology

Threshers are slightly taller on average than humans with dense, almost Dwarvish builds. They lack any body hair. Their skin is bleached-bone pale, lacking even the flush of rosy cheeks, and their glossy patches of chitinous armor are a near-white pearlescent color, though some have hints of iridescent or seashell-pastel hues. Threshers will usually avoid having any strong contrasting colors or patterns on their skin and chitin; clothing style can vary widely, however, and jewelry is common as a statement of personal wealth and value.
Each thresher has a unique pattern of chitinous armor covering parts of shoulders, back, head, neck, sometimes including their ribs, hips, and thighs. There is significant variance even in the same family of how much coverage a thresher has and in what patterns or shapes. Thresher faces are human-like, though far enough diverged from actual humans that no recognizable ethnic traits remain in their features. Their faces are often framed with chitinous plating, almost like a close-fitting helmet, and occasionally they'll sport mandible-like growths along the outside of their jawlines. Nearly all threshers have a pair of twiggy antennae, and many of them retain humanoid ears.
Thresher faces, unfortunately, lack the symmetry that most humanoids use to determine physical beauty. One half of their face is rarely a perfect mirror of the other, whether it's a chitin-covered eye socket, a mouth that is more mandibular on one side, or even one eye broken into a trio of small, perfectly round orbs. This unusual visage is the source of most humanoid discomfort around them.
Threshers have two pairs of arms: a deteriorated humanoid pair that hunch forwards and inwards, and an overlapping pair of mantis-like appendages that project almost from the upper-back of the shoulder and then angle forwards and over the other arms. Their upper arms are powerful but not terribly flexible, while their inner arms are weak but very dextrous.

Society

Threshers have built productive, industrious city-states in pockets of land between other races' kingdoms or territories. They favor stone and metal as building materials and have developed a reputation for an uncanny cleanliness even in public spaces, which contributed to their settlements' nickname, the White Cities.
Threshers are undeniably a people of order. Their economy is bustling, their civil structure is robust, and their modest military is well-disciplined and sharply trained. Much of their trade is brokered by contracts and agreements, and it's fairly rare that a thresher soldier is deployed in a situation that is not peace-keeping or disaster response. They are not war-mongerers and will actively seek peaceful accords whenever politics with other cities or peoples seems likely to cause trouble.
Individual threshers are most content when the greater machine of their society is working as intended. They are easily bored and tend to place most of their self-worth in what they can do, especially in regards to how they can contribute to their community and city. They enjoy being industrious but do not lament having clear roles or limited purview--they tend to be specialists, not generalists, and may become distressed when presented with too many options.
The White Cities always welcome visitors, be they travelers or traders. The poorest thresher inn is more comfortable and clean than all but the most expensive inns elsewhere. The streets are always safe, no matter day or night. Crime does not seem to exist amongst the threshers, and anyone attempting to import trouble will find themselves quickly exported or vanished. Even new citizens to the city or settlers to the surrounding farmlands are welcomed, provided they stay within thresher social structures and pay their dues.

Racial Features for Players

It is possible, albeit extremely rare, for an individual thresher to break from their monocultural society. They must actively fight against their indoctrination in order to leave everything they know--and they must make that same choice day after day, without their resolution wavering. Their weapons in this internal struggle are their crystal-clear logic and reasoning, as well as whatever emotional and social attachments they can develop outside of their homes. Even parted from their society, threshers are intensely social people and will almost always seek out the company of others when possible. Thresher adventurers usually make a point to set themselves apart visually from their brethren with high-contrast designs painted or tattooed onto their bodies.
Threshers generally do not have innate magical abilities, as their strange bodies render them somewhat resistant to the physical effects of magic. Those who pursue a magical path must do so via study (wizardry, artifice), gifts (divine boons), or fair trade (pacts with powerful entities). Threshers who identify as bards, druids, and sorcerers are extraordinarily rare.
Ability Score Increase. Your Charisma score increases by 2. Your Strength score increases by 1.
Age. Threshers have a lifespan comparable to humans.
Size. Threshers tend to be somewhat taller than humans, averaging 6-6.5' high. Your size is Medium.
Speed. Your base walking speed is 30 feet.
Languages. You can speak, read, and write Common, Ixt (the common human language of southern Feraweth), and Dwarvish.
Magical Resistance. You have resistance to all types of magical damage except for psychic and necrotic.
Natural Armor. Your chitinous plating protects you. When you aren't wearing armor, your AC is 12 + your Dexterity modifier. You can use your natural armor to determine your AC if the armor you wear would leave you with a lower AC. A shield's benefits apply as normal while you use your natural armor.
Four-Armed. Your unique physiology has both advantages and drawbacks.

Specialty Armor. You cannot wear standard forms of shoulder, chest, or torso armor without modifying it for your physiology. Cloaks, bracers, gloves, and jewelry can still fit.

Scythe-hands. Your praying-mantis-shaped upper arms end in scythe-like "hands" with a single small "thumb" that acts as a pincer.

Your scythe-hands have Disadvantage on any Dexterity checks and saves that involve fine motor control, subtlety, and delicate motions, such as using thieves' tools, opening a potion bottle, or writing a letter.

You can wield most melee weapons with your scythe-hands, but not ranged weapons.

Your scythe-hands are natural weapons, which you can use to make unarmed strikes. If you hit with it, you deal piercing damage equal to 1d4 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.

Humanoid hands. Your weaker lower arms end in bony but dextrous humanoid hands.

Your humanoid hands and arms have Disadvantage on any Strength checks and saves, such as grappling, climbing a rope, or holding on to a heavy object.

In order for your humanoid hands to wield a weapon, it must have the Finesse and Light properties.

Lend a hand. If you use both your scythe-hands and humanoid hands in concert to perform an action, the Strength and Dexterity disadvantages will be canceled out.

Hivemind. Your partially-insectoid origin has both blessed and cursed you with a greater awareness of the similar minds around you.

Limited telepathy. You can communicate in simple images and projected emotions to any number of threshers within 30' of you. You cannot knowingly lie with this method of communication.

Lurking whispers. Whenever you roll a natural 1, the ever-present whisper of the hivemind surfaces and redirects your action. Your DM can determine what happens, but here are a few suggestions:

On a natural 1 attack roll, reroll the dice to attempt to attack your nearest non-thresher ally as a free action. If no allies are within range, you must target yourself.

On a natural 1 saving throw, you immediately fall prone.

On a natural 1 ability check, you are stunned for 1 round.