The Atlantean culture has always circled around the advancement of technology to the point that they would fuse technology with their own bodies making them semi-cybernetic. Atlanteans would replace one of their body parts with a mechanical one in order to give them an advantage. To power their technology the soul crystals were invented, embued with the power of a willing soul, a crystal could provide enough power to use their new cybernetic appendage. Every Atlantean child has a crystal placed into their chest at birth and their own soul (if willing) is fused to it. If a person was on the verge of death and willingly they too can fuse their soul into another crystal, increasing the power of the user.  The souls must be willing or else the crystal will become unstable from the souls attempting to escape. If a crystal was to become unstable it would cause 3d6 force damage per unwilling soul that has been trapped.

     The Atlanteans would continue to push the limits of their technology, using the ability of the crystals they would attempt to bring life back from the dead by embuing the soul from a crystal into a mechanical body. This act enraged the god Archon and out of fear for how far the Atlanteans could go with their technology he destroyed the city of Atlantis. After the great cataclysm a crack forms where the entrance to Agartha once stood. Hoping to find refuse the Atlanteans enter Agartha where they see a vast world occupied by all non-human races, creatures, and monsters. Working with the civilizations that thrived in Agartha, the Atlanteans would rebuild their home, forming the city of New Atlantis. Due to their culture, all Atlanteans start off as artificers but can multi-class over time into other classes that fit their character. An Atlantean can have one of their body parts removed and replaced with a mechanical version that can either provide them with a bonus or an additional feat that correlates with the body part (these bonuses and or feats are up to your DM's discretion). The soul crystal resides in the sternum and protrudes slightly thru the skin. The soul crystal glows with a bluish-green light and can take any shape the player wishes. When a body part is replaced, wires are run from the mechanical version to the crystal under the skin, the wires will glow with the same bluish-green light. 

 

Soul Tap

     A collection of willing souls reside within the crystal embedded in your chest, with concentration you can tap into these lost souls and commune with them in order to gain guidance on a specific task. You can choose the soul you wish to commune with but they can only give you the knowledge they have. Only one soul can be talked to once per day and the character can only ask one question from the soul, any conversation after is up to the decreation of your DM. 

Crystalline Focus

The power of the souls that reside inside your crystal can be harnessed giving you the ability to use the spell Epicenter of Major Force. You form a pulsing ball of light with both your hands, which explodes in all directions with you at the center. All creatures within 5 feet of you take 5d6 force damage and must make a Strength saving throw or are stunned until the end of their next turn. A creature that succeeds in the saving throw is not stunned. Due to the immense amount of concentration needed to perform this spell it can not be used again until a long rest is completed. 

Articifier Engineering

After years of trying to master your craft, you have gained the ability to add a feat to your mechanical body part. 

The Souls Calling

The souls of those who live within the crystal embedded in your chest protect you as much as you protect them. When the need arises the souls grant you the power of the spell etherealness at the 8th level. You step into the border regions of the Ethereal Plane, in the area where it overlaps with your current plane. You remain in the Border Ethereal for the duration or until you use your action to dismiss the spell. During this time, you can move in any direction. If you move up or down, every foot of movement costs an extra foot. You can see and hear the plane you originated from, but everything there looks gray, and you can’t see anything more than 60 feet away. While on the Ethereal Plane, you can only affect and be affected by other creatures on that plane. Creatures that aren’t on the Ethereal Plane can’t perceive you and can’t interact with you unless a special ability or magic has given them the ability to do so. You ignore all objects and effects that aren’t on the Ethereal Plane, allowing you to move through objects you perceive on the plane you originated from. When the spell ends, you immediately return to the plane you originated from in the spot you currently occupy. If you occupy the same spot as a solid object or creature when this happens, you are immediately shunted to the nearest unoccupied space that you can occupy and take force damage equal to twice the number of feet you are moved. This spell has no effect if you cast it while you are on the Ethereal Plane or a plane that doesn’t border it, such as one of the Outer Planes.
At Higher Levels: When you cast this spell using a spell slot of 8th level or higher, you can target up to three willing creatures (including you) for each slot level above 7th. The creatures must be within 10 feet of you when you cast the spell.