Since the creature has to attack each turn, it isn't a great answer to opposing commanders, like an Imprisoned in the Moon is, but you disrupt decks that rely on a key card or two when you keep a threat out of your enemys hands
My Three Kingdoms for a horse (Get it?)
The original idea for Alara Reborn , besides having all gold cards, is that it would focus on two-color ally pairs
With Mirkwood Bats in play, each time a token is created or sacrificed, each opponent loses 1 life
That said, it's not clear who put the item up for auction, or if it was even one of the original recipients
You do need to tailor the deck to contain the Necro but once you can support it it gives you immense power