Squealing Devil

Oracle Text

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)

When Squealing Devil enters the battlefield, you may pay X. If you do, target creature gets +X/+0 until end of turn.

When Squealing Devil enters the battlefield, sacrifice it unless B was spent to cast it.

Card Rulings

5/1/2006 For this creature to not be sacrificed, must have been spent on the mana cost. It doesn’t matter if is spent on .
5/1/2006 You choose the value of X as Squealing Devil’s ability resolves. X can be 0.
5/1/2006 If this enters the battlefield in a way other than announcing it as a spell, then the appropriate mana can’t have been paid, and you’ll have to sacrifice it.