Health
From Hades 2 Wiki and Guides
Useful Pages:
Nocturnal Arms, their Aspects & Upgrades
All the Boons
Hades II Guides
Health represents amount of damage you can take before losing. The maximum amount of Health is governed by 
Max Health.
There are multiple ways of restoring Health, but in most cases it's better to avoid the damage altogether.
You can increase Max Health by collecting 
Centaur Hearts