Plot Armor

Not to be confused with taking the script and wrapping it around your body.

If someone, a main character, should have died but didn't, they won the big game when all seemed lost, or anything else that's super useful for someone, that's Plot Armor in action. Plot Armor means when something plot-convenient happens to someone who's important to the plot so that nothing can mess the plot up despite what happened was obviously "rigged" by the writers.

Ex Machina moment breeds such as Plot Ex Machina are quite common with Plot Armor, but UnTrashes like Set Destiny can be used in its aid as well.