Paladin better get some big spell support to make this work, zilliax just seems a lot less restrictive. Nobody uses stuff like lay on hands or avenging wrath currently, the highest cost spells used at the moment are steed and MAYBE shrink ray. Control paladin cards incoming to support this?
So I have to play 15 mana worth of spells to get this to 10 mana in some kind of Paladin control deck? Or try to pull this off of Prismatic Lens before drawing it with only a few or no other minions in my deck? Paladin better get some seriously good spells this expansion or I don't see how this card can work. The effect doesn't seem worth the effort.
I think getting this card down to 0 cost is going to be very hard... but even if you only played... say... 2 spikeridged steeds, 2 consecrates.. you've got yourself a nice little 5 mana Shirvallah the Tiger. I honestly think it has some potential, but its tough to say. If you can get it too 0 mana somehow you could pull some crazy cube shenanigans too.