Your crystalline body holds strong against attacks but isn't invulnerable. You can take a few blows with stride before feeling your crystalline skin crack. Once you take a long rest you are able to focus enough to reform and repair your crystalline exterior. 

As a reaction, you become resistant to bludgeoning, piercing, slashing, and radiant damage for the duration of one attack. You may use this feature a number of times equal to your proficiency bonus before a long rest. 

Crystal Grafters living amongst society will eventually find themselves needing a more effective way of communication with others. By practicing the reflection of light off their bodies and using the knowledge of humanoids Crystal Grafters will create a humanoid persona to interact with others on their behalf. While visually uncanny to a normal humanoid, any sound will only ever come from the Crystal Grafter itself. This is usually done either through a grafted body part or by vibrating their bodies in just the right way to replicate words. 

You may use this feature under any amount of light to create a projection of an illusionary humanoid persona to interact on your behalf. The projection is hard to maintain while moving quickly and will require concentration. Max range of 5 feet. 

You create a crystalline copy of a body part or object and implant it into your body as long as you gather enough crystal material. You can change your form drastically enough to look and physically function completely differently with enough implants. While not in a Humanoid form you are considered the Abberation creature type.

There is a limit however to how much one brain can handle. You can only control so many limbs at once, and therefore cannot gain any extra attacks solely through the use of this feature. 

Using crystal material reshape yourself into a new form over a long rest. You will need more crystals for more drastic changes. Talk to your DM about what seems fair. 

You may gain one mechanical benefit from this trait. At level 5 gain another mechanical bonus. Swap out any undesired bonuses during a long rest.
Here is a list of example bonuses from this trait. Feel free to talk with your DM about coming up with more options. 

Crystal Spike; You implant spikes within yourself and prepare them for future foes. As an action launch them at a foe at a range of 30/120 dealing 1d8 + Constitution damage. Use your Constitution modifier to hit (1d20+Con). Every 5 levels you may launch another projectile. The damage type is chosen when the spikes are implanted within yourself. Use this feature up to your constitution modifier per long rest (minimum of 1).  

Nimble Climber: You have a climbing speed equal to your walking speed. 

Limb Shield; Use a reaction to being attacked and raise your AC +1 until your next turn.  

Constructed Glide: You've structured yourself in such a way that can slow your fall and allow you to glide. When you fall and aren't incapacitated, you can subtract up to 100 feet from the fall when calculating falling damage, and you can move up to 2 feet horizontally for every 1 foot you descend.

Natural Weapons: Creating claws and the alike have granted easy access to a weapon should all else fail. Your claws deal 1d6 + Constitution slashing damage.