Wrenhart's Last Stand

You siphon some of your life force into a shimmering shield of light around yourself. Sacrifice any number of hit points (up to your current total -1) when you cast the spell, and you immediately gain twice as many temporary hit points. You must leave yourself at least 1 "real" hit point. While any of those temporary hit points remain you gain advantage on Dexterity and Constitution saving throws.

Remaining hit points disappear when the spell ends. The spell ends immediately if all the temporary hit points are lost.