True Sadist

You gain ecstasy from pain. 

When you drop below 20 HP you gain Advantage on all Saving Throws

When creature gets a Critical Hit, you gain Advantage on your next Attack Action 

When you drop below 10 HP you gain 10 extra feet of movement, and you are automatically immune to opportunity attacks

If you die, roll a d20. If you get a 20, you heal to 20 HP and your character MUST say, “Yay! More pain!” This is once per long rest.