User blog comment:Zilla4444/AP Version of Black Cleaver/@comment-2095407-20120624085114

I say lets wait till new Haunting Guise comes out with upgrade. I myself would really prefer flat penetration on my mages instead of per spell reduction. Why? Some mages dont have that low cooldowns on spells. Not everyone is Cass, Karth or Eve. Someone like Veigar sould land all his spells to apply full stacks and run around retardedly for cooldowns. Active part apply is not an option, I cant see it being in game. Flat penetration would benefit everyone a lot more. Penetration does not requires range, works fully on aoe and globar spells, gets target only to 0 MR but that is not OP, because is works only for you alone, not all team and you have to invest for it.

Better wait, I feel new Guise will be really good, just like Grail ;)