Indomitable Will

You have honed your will to the finest edge, and stay focused in the face of death, learning techniques that grant you the following benefits:

• You may reroll a failed concentration check. This ability resets after a short or  long rest.
• You may maintain concentration on a spell, even when knocked unconscious. If you choose to do so you have disadvantage on all death saving throws and take two levels of exhaustion if you are revived in any way. You must still make concentration checks immediately after a death saving throw. If your death saving throw was unsuccessful, you have disadvantage on the concentration check.