Hmmm... The idea of reviving dead creatures has come up alot.
I can dig up the quote if needed, but unfortunately I believe Zanz has more or less nixed the idea of a graveyard.
This card only affects the last ally to fall, so a full fledged graveyard isn't needed... but it may still be a bit to close.
On the other hand, maybe you could pattern the ability to be something akin to Graviton Salvager, but for creatures.