Hydra's Resilience

You have developed traits similar to that of a hydra, granting you the following benefits:

• Increase your Strength or Constitution by 1, to a maximum of 20.
• You have advantage on saving throws against being blinded, charmed, deafened, frightened, or stunned. In addition, you gain an extra reaction that can be used only for opportunity attacks. If on a single turn, you take an amount of damage equal to or greater than your proficiency bonus times your Constitution modifier this feature ceases to function. At the end of your turn, if this ability doesn't function and you have not taken fire damage since the end of your last turn, you regain a number of hit points equal to half your Constitution score and this ability begins functioning again.