You let your emotions overwhelm you, unleashing your long suppressed powers you have denied or been unaware of possessing. 

Can be used once per long rest without fail (safe use). If it is used more than once, it takes a great toll on your body and will afflict the user with an exhaustion level equal to the number of uses exceeding the safe uses, when the effect is active. Every level gained you are automatically able to cast any spell of the chosen damage type your class gains access to, whilst under the effect. You must not have the spells known. However, you cannot cast any damaging spell outside of this form if this feat is chosen. Moreover: you cannot cast any evocation spell of another damage type from your regular spell book when the effect persists. 

• You have disadvantage in wisdom saving throws and ability checks whilst under this effect. 
• You have disadvantage in intelligence saving throws and ability checks whilst under this effect.
• You have advantage in constitution saving throws and ability checks whilst under this effect.
• You have advantage in dexterity or strength (whichever is highest) saving throws and ability checks whilst under this effect.

 Duration: 1 minute

Casting time: 1 bonus action or 1 reaction. Always triggers automatically and involuntarily when fallen below half HP or in the event of a strong negative emotional occurrence. If you wish to suppress this involuntary trigger, make a charisma saving throw. To succeed, this saving throw must exceed your own spell DC. 

Choose cold, fire, force, lightning, necrotic, psychic or thunder damage. Until this spell ends, you gain the following benefits:

• You may make an attack as a bonus action.
• You have +1d6 damage of the chosen type to all your weapon attacks.
• Spells you cast that deal the chosen damage type deal +1d6 damage of that type. 
• You have immunity to the chosen damage type.
• Your known spells are replaced by another list as appropriate.

Level 10: Elemental spell and weapon damage is now +2d6. 

Level 11: Duration increased to 5 minutes.

Level 12: You can freely switch between the different elemental states. Elemental spell and weapon damage is now +3d6.

Level 14: You can now use this effect two times every long rest without suffering any level of exhaustion. Elemental spell and weapon damage is now +4d6.

Level 16: You are now adept to this form and no longer have disadvantage in saving throws and ability checks. Elemental spell and weapon damage is now +5d6.

Level 18: You have mastered this form and can stay in it permanently if you so which, in addition you can now also freely switch in and out from it at any given point (no action required). Elemental spell and weapon damage is now +6d6.

Elemental spell and weapon damage  is increased by an additional d6 every other level above level 19.