Vallar of Failed Duty

At the beginning of your upkeep, if Vallar of Failed Duty is in your graveyard, you may return it to the battlefield tapped.
Vallar of Failed Duty attacks each combat if able.
When Vallar of Failed Duty deals combat damage to an opponent, exile it.
"I failed to protect my lord. I failed to protect my honor. I failed to die. I will not fail again."