Hardy Adventurer A5E
When you take this feat, you gain a number of hit points equal to twice your level.
Whenever you gain a new level, you gain an additional 2 hit points to your hit point maximum.
During a short rest, you regain 1 additional hit point per hit die spent to heal.
Source: Adventurer's Guide (EN Publishing) · License: Creative Commons Attribution 4.0 / OPEN GAME LICENSE Version 1.0a details