Diehard

Your will to live makes you unnaturally difficult to kill. You gain the following benefits:

• When you are reduced to 0 hit points, you can make a Constitution saving throw with a DC of 10 + the damage taken. On a success, you are reduced to 1 hit point instead. You can’t benefit from this feature again until you finish a long rest.
• You make death saving throws with advantage.
• When you succeed on death saving throws three times, you regain 1 hit point. You can’t benefit from this feature more than once in a single combat encounter.