Protected Players

Plot Armor

...Luck...

Reduce Damage

The Lower HP you are the less damage they will deal

Disadvantage

When low, The NPC will get Disadvantage on checks

Increase Odds

Players will often get advantage when in a risky place

Anti-Crit

NPC will not be allowed to Crit players when a Player is low

Rule Bending

Sometimes rules are bendt to keep players alive

Targeting

The lower HP a player has the lower the chances are of them getting Targeting by an NPC

Death Saving Throws

:/

Immune System

Roll advantage on Diseases that will kill you