This card is very underpowered. You would need at least 8 skeletons out before this card is even worth it's cost.
Well, if you have fractal, just spam your screen with spraks or photons. then, with RoF, Destroy the whole field and you gain plenty of skeletons.
Pandemonium is a -much- better substitute, assuming that you get the correct procs (Fire Lance, Ice Bolt, Shockwave, etc.) to damage the creatures to generate skeletons for the card.
Making it a passive is a great concept though.

I'm all up for seeing what other abilities could be applied to it in addition to a crazy attack boost from its passive skill. ^^