Squealing Devil

Creature - Devil 2/1, 1R (2)
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.¹
Illus. Matt Cavotta

Gatherer Card Rulings [Nov 2009]

• 5/1/2006: For this creature to not be sacrificed, {B} must have been spent on the {1}{R} mana cost. It doesn't matter if {B} is spent on {X}.
• 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.  

Format Legality	Legal in Vintage, Legacy, Extended Banned in Standard
Printings (1/9)	Dissension (Uncommon)