Grit (5e Feat)

When your back is to the wall, you are at your most dangerous. You gain the following benefits:

Increase your Constitution or Wisdom score by 1, to a maximum of 20.
You have advantage on saving throws made to resist or remove Fear and Madness effects.
While you are at or below half of your hit point maximum, you add half of your proficiency bonus to all of your saving throws.
When you are reduced to 0 hit points but not killed outright, you can make your choice of either a Wisdom or Constitution saving throw. The saving throw DC is equal to 10 or ½ the damage received, whichever is higher. If the damage was from a critical hit, this saving throw is made with disadvantage. On a successful save you choose to remain at 1 hit point and immediately expend any number of your available hit die. Roll each die to be used. Add your character level and your constitution modifier to the result, you gain an amount temporary hit points equal to the result. These temporary hit points last for one minute. You must finish a long rest before you can use this feature again.

Special: "Madness Effects" include checks related to a character's sanity.