Your Constitution increases by 2

During a long rest, you may replace or add a body part. They may contain certain properties such as a cannon arm or wings. You can only have a maximum of 6 limbs at a time and armors cannot be worn normally and must be turned into part of your body during the long rest.

Your soul is affected by the material of your core.

Elemental Core - Fire: Core purely made of primordial fire, you are resistant to fire attacks.
Elemental Core - Ice: Core purely made of primordial ice, you are resistant to cold attacks.
Elemental Core - Lightning: With a core purely made of primordial lightning, you are resistant to lightning attacks.
Diamond Core: Core made of diamond, you have +1 to AC.
Solid Aether Core: Core made of Solid Aether, you gain +1 to wisdom and intelligence.