Strength of the Grave

Starting at 1st level, your existence in a twilight state between life and death makes you difficult to defeat. When damage reduces you to 0 hit points, you can make a Charisma saving throw (DC 5 + the damage taken). On a success, you instead drop to 1 hit point. You can't use this feature if you are reduced to 0 hit points by Radiant damage or by a critical hit.

After the saving throw succeeds, you can't use this feature again until you finish a long rest.