Top that off with an exceptionally strong attack trigger, to put a +1/+1 counter on each of your Vampire creatures when he attacks, you have yourself a constantly growing army to take down any opponent
Its cheap cost makes it powerful, but its sorcery speed leaves the tutored card vulnerable to mill or shuffle effects before you have an opportunity to draw it
The cost reduction also applies to card-draw spells like Reckless Impulse and Wrenn's Resolve, allowing you to churn through your library with startling speed
Sure, you sometimes help your other opponents, but it should draw a lot of focus off your creatures and benefit you as well
The most popular of these commanders is Goreclaw, who itself can fulfill the Ferocious requirement, while also making all of your power 4 or greater creatures better attackers, while also making them easier to cast
Then again, Ive never seen an angel before in real life so you never know