You may cast certain acid spells. However, you now dissolve any objects you come into contact with. To prevent this, you must make a Constitution save with a DC equal to your infection level. These do not expend spell slots and can be cast throughout the day.
Every day, you must make a Constitution save. If the roll is less than 7, your infection increases by 1 level. If the roll is more than 13, your infection drops by 1 level.
When you gain this feat, you roll a d20 to determine your infection level. If your infection level reaches 20, you are permanently in the rage mode until you lose 1 infection level. If your infection level reaches 0, you keep the boon and are no longer bound by the condition.
Spells like greater restoration or heal reduce the infection level by their spell level. A medicine check with a DC equal to the infection level can reduce it by 2.
A bit unspecified. What "certain acid" spells? What is rage mode? How often can the medicine check be made? What does the acid dissolve? Must the character be naked?