You may increase one of your ability scores by 2, and another by 1; or three of your ability scores by 1

You have proficiency with tinker's tools.

You are a construct.

Your body is encased entirely in metal and other durable components, making you far less fragile than other creatures; granting you the following features:

- You are immune to poison damage and the poisoned condition. You are also immune to disease.

- You need to sleep, and magic cannot put you to sleep.

- You don't need to breath, and cannot eat; but must refill a water tank beneath your plating regularly  to maintain your biological mainframe. Ingestible items such as potions, and alcohol, do not benefit you as they would other creatures and may have adverse effects at your DM's discretion.

- You treat your exhaustion as 1 level lower.

Your body is covered in interwoven porcelain and metal plating, making you for more durable than other living things. While this plating is closed, your AC is increased by an amount equal to your proficiency bonus, rounded up; and you are resistant to piercing and slashing damage. However, each time you take bludgeoning damage from an attack, you take an additional amount equal to the damage modifier of the attack.

But, in order to repair yourself, intake water, or change your programming; your plating must be open. You or your user can open or close your plating at any time using an action, your user must be within 5ft of you to do this. While your plating is open, your intricate inner workings and biological components are exposed, your movement speed is 0, and you are vulnerable to all damage (this ignores your immunity to poison damage).

If the Mending spell is cast on you, you can spend a Hit Die, roll it, and regain a number of hit points equal to the roll plus your Constitution modifier (minimum of 1 hit point).

Otherwise, regaining hit points requires you to open your plating and undergo repairs. While your plating is open, any creature that has proficiency with tinkers tools can spend any number of hours repairing you. For every hour you spend being repaired in this way, you can roll a number of hit dice equal to the proficiency bonus of the creature repairing you, add your constitution modifier (minimum of +0); and regain a number of of hit points equal to the total. Doing this does not spend the hit die.

You are treated as being a humanoid for the purposes of enchantment spells and abilities which would charm, or frighten you.

You are also built in with an intrinsic set of psychic programming, which is set by your user. You and your DM can work together to decide who your user is, if you have one, and what your current and pre-existing programming is. You are always considered to be charmed by your current user, and have disadvantage on saves to ignore their direct commands.

Additionally, you have advantage to resist spells and effects which would cause you to defy your programming, and disadvantage against effects that would fall in line with it. 

When you take a long rest, you spend at least 6 hours in an inactive, motionless state, instead of sleeping. In this state, you appear inert, but you remain conscious. Resting in this way allows you to regain Hitdice and exhaustion as other species do. But you do not regain hit points.