The More Hearts Gene increases the entity's maximum health by 20 points (10 hearts).
It can be mutated into More Hearts II to further increase the maximum health by another 20 points (10 hearts).
Obtaining
By default, you can get it from these sources:
- Enderman: 1/9
- Iron Golem: 2/19
- Ravager: 3/17
- Warden: 5/10