race features:
Monstrosity. Your creature type is monstrosity, rather than humanoid.
Size. Your size can be Small instead of Medium.
Chameleon Carapace. While you aren't wearing armour, your carapace gives you an Armour Class of 13 + your Dexterity modifier. As an action, you can change the colour of your carapace to match the colour and texture of your surroundings, giving you advantage on Dexterity (Stealth) checks made to hide in those surroundings.
Darkvision. Accustomed to twilit forests and the night sky, 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 colour in darkness, only shades of grey.
Secondary Arms. You have two slightly smaller secondary arms below your primary pair of arms. The secondary arms can manipulate an object, open or close a door or container, pick up or set down a Tiny object, or wield a weapon that has the light property.
Sleepless. You do not require sleep and can remain conscious during a long rest, though you must still refrain from strenuous activity to gain the benefit of the rest.
Thri-Kreen Telepathy. Without the assistance of magic, you cannot speak the non-thri-kreen languages you know. Instead you use telepathy to convey your thoughts. You have the magical ability to transmit your thoughts mentally to willing creatures you can see within 120 feet of yourself. A contacted creature doesn't need to share a language with you to understand your thoughts, but it must be able to understand at least one language. Your telepathic link to a creature is broken if you and the creature move more than 120 feet apart, if either of you is incapacitated, or if either of you mentally breaks the connection (no action required).
A thri-kreen resembles a giant praying mantis. They have exoskeletons over their entire bodies. They have six limbs protruding from their thorax: two for walking and four for use as arms, ending in four-fingered claw-like hands capable of tool- and weapon-use. Their insectoid heads have two black, multi-faceted compound eyes; two small antennae sprouting from the top; and a complex jaw structure with large sharp mandibles. It is extremely difficult to distinguish the males and females.
The carapace of a thri-kreen is typically a sandy yellow in hue, but could vary from a sandy brown to a pale green colour, as best suited the environment. This enables thri-kreen to blend in with the dry savannas and grasslands they dwell in.