Survivor

You use every last ounce of energy to survive, even in the worst of circumstances.

When you are reduced to 0 or fewer hit points, you can use your reaction to move up to your Speed before falling unconscious. Moving in this way doesn't provoke opportunity attacks.
On the first turn that you start with 0 hit points and must make a death saving throw, you make that saving throw with advantage.
When you take massive damage that would kill you instantly, you can use your reaction to make a death saving throw. If the saving throw succeeds, you instead fall unconscious and are dying.
Medicine checks made to stabilize you have advantage.
When a creature successfully stabilizes you, at the start of your next turn you regain 1 hit point. Once you have used this feature, you can't use it again until you finish a long rest.