Knight of the Unholy Vow

Whenever you sacrifice a creature, Knight of the Unholy Vow gains +2/+0 and Fear until end of turn.
You may sacrifice a creature at any time you could cast a Sorcery to gain 1 life or add {b} to your Mana pool.
"I pledge myself to my Lord, and embrace the suffering he offers, so that I can bring it to others, and share with them the great and sacred truth of Death"
-The Unholy Vow, chapter one