Creation

Son of Pyg was created by Grant Morrison, and has been illustrated by artists Chris Burnham and Cameron Stewart. 
 

Major Story Arcs

Batman Incorporated. 

Johnny Valentine is been tracked down and pursued by Batwoman through Kane's Kolossal Karnival for the murder of three U.S Marines. During the chase, 

Jake Kane contacts the vigilante and tells her the targeting of the Marines had been very precise. In fact, each bullet's position in each victim spelled out a Braille letter - "Oscar",  "Roger" and "Bravo" (spelling out the three letters that make up the word "oroboro", a symbol used by Leviathan and also a military codeword for "some kind of ultimate weapon.")  
 
Johnny calls for backup but is directed to the ghost house, where Batwoman is confronted by an imposter of the original mantle, Kathy Kane. After that confrontation, Valentine is long gone.

Batman Incorporated: Leviathan Strikes!

Johnny Valentine returns as the head of a Leviathan ritual at St. Hadrian's, an English all girls boarding school, training the students to become assassins. The ritual is held for the then Batgirl, Stephanie Brown, who had infiltrated the school.
 
Johnny now wears a melted Pyg mask with red eyes. He explains how his real name is Janosz Valentin and that he is the son of Lazlo Valentin, hence his new pseudonym - Son of Pyg. He claims his father taught him the ability to not feel pain, of which he demonstrates by skewering his hand with a sewing needle without flinching. Janosz goes on to claim how he will teach Stephanie the same ability and how to kill when told without hesitation. 
 
The ritual is halted when he admits he knows someone has betrayed them, as a fight breaks out between him and Batgirl. Stephanie escapes and groups up with Batman, who defeats Janosz and unmasks him. 
 

Powers

  
Janosz shows no display of powers other than the ability to feel no pain (of which he proves with a sewing needle). He is also a skilled gunman, capable of causing precisely placed shots.