Boon of Fortitude

Boon of Fortitude
Feat
Prerequisite: Level 19

You gain the following benefits.
Fortified Health.
Your Hit Point maximum increases by 40. In addition, whenever you regain Hit Points, you can regain additional Hit Points equal to your Constitution modifier. Once you've regained these additional Hit Points, you can't do so again until the start of your next turn.

Source: Player's Handbook (2024) (XPHB), page 210