This... is a great card. It's the kind of card I think this game needs more of, especially Darkness. The concept is just... brilliant. Great synergy with the god damned hated by everybody dusk shield and the Vampires, making Darkness a very hard to kill element.
Also, this card is the perfect buff for Stall decks. You're getting pwned by that epic ever-growing Lava Golem or that Steam Machine? This card is exactly what you need Now at only 24 electrum a piece!
Now that I think more about it, it might be a little bit on the OP side. Almost all decks these days are using some sort of buff or another for their creatures. 1 or 2 more cost should fix it though.
The only downside I could see with this card is that it's a card that doesn't help much in early game, as it doesn't damage, heal, or CC's directly. Then again, this could be easily solved by the aforementioned Dusk Vampire combo.
So, to sum it all up, I think this idea is awesome and will likely go a long way in the Card section, with relative speed. Congratulations for your epic idea, and I sincerely hope (no pun intended) this goes all the way to the Reliquary. Good luck, and keep it up!