What is the word/phrase for the phenomenon that heroes and (particularly) heroines never die in a movie?

When watching movies, it is common to see heroes and (particularly) heroines surrounded by dozens of enemies but getting rid of them anyway. How do native speakers of English describe this phenomenon?

Solution 1:

The hero usually wears a plot armor.

Plot armor: Sometimes referred to as "Script Immunity" or a "Character Shield", Plot Armor is when a main character's life and health are safeguarded by the fact that he's the one person who can't be removed from the story. Therefore, whenever Bob is in a situation where he could be killed (or at the least very seriously injured), he comes out unharmed with no logical, In-Universe explanation.