Tempest Lord

You have become to in tune with the forces of the tempest that it now follows you around, and bows to your command. You are the one true ruler of the skies.
You gain the following benefits

Storm of Vengeance
As an action you may cast Storm of Vengeance directly above your head, requiring no spell slots or concentration. This has 3 charges and lasts 5 minutes per charge, recharging all charges after a long rest. Only round 3 and 5 effects are present when casting Storm of Vengeance through this boon, but both effects run throughout the entirety of its duration. The user, and all allies of the person with this boon are immune to the effects of Storm of Vengeance casted through Tempest Lord.

Thunderous Rally
Upon reaching 0HP, instead of rolling death saves the user of this boon transforms into a CR23 Elder Tempest. This effect lasts for 3 rounds, and the elder tempest retains all benefits given by the Tempest Lord boon. After the 3 rounds, if the Elder Tempest has HP remaining, the user appears in a safe, unoccupied space, retaining all HP that the Elder Tempest had left. If the Elder Tempest is reduced to 0HP, the effect ends on the user and they will roll death saves as normal. Thunderous Rally can only be used once per long rest.

Other
When the user takes thunder or lightning damage, they instead heal, equal to half of the thunder and/or lightning damage dealt. This can overflow into THP, to a max of half of the users max HP.
You gain control of the weather, as in the spell Control Weather