You gain proficiency in 3 tools or skills of your choice.

You cannot benefit from the effects of a normal healing spell, but if the mending spell is cast on you, you gain 2d6 hit points.

You are immune to any spell or effect that would alter your form against your will and any attempt to do so is wasted.

Your body has built-in defensive layers, which can be enhanced with armor:

You gain a +1 bonus to Armor Class.
You can don only armor with which you have proficiency. To don armor other than a shield, you must incorporate it into your body over the course of 1 hour, during which you remain in contact with the armor. To doff armor, you must spend 1 hour removing it. You can rest while donning or doffing armor in this way.
While you live, the armor incorporated into your body can't be removed against your will.

The method of how you are powered. (This has no effects so if you don't want this, you can ignore.)

Do what you must with this, if you don't care then you can be on your way but if you want to have some fluff or stats for this, please make your own version for this race and edit this species trait.

You have Darkvision with a range of 60 feet.

You have Resistance to Poison damage. You also have Advantage on saving throws you make to avoid or end the Poisoned condition.

Your Hit Point maximum increases by 1, and it increases by 1 again whenever you gain a level.