Blessing of Hades

You who have faced the trials of Hades and proven that death is something to be faced instead of feared. You who have passed through the shadows and struggles of the temple. You who have proven a dedication that transcends mortal bounds: you have gained the Blessing of Hades and consequently, the old god's favour. 

When faced with the very real possibility of death, you grit your teeth and stand your ground. Attack rolls performed when you are under 25% health are done with advantage.