History

Born in the town of "Almost Reno", Zach is one of many children who were born by The Damocles Foundation  splicing the x-factor gene of human mutants with the equivalent gene from Deviants .  
 
Growing up, all children manifested different abilities but when the resulting powers were deemed unstable, the town was quarantined and only Zach and little Mary were left behind. Even though his mutation caused him to lose his higher brain functions which made him appear mute at times, he was still deemed a mild success as his powers never burned out.
 
Him and Mary bonded fast and they defended each other from agents of The Damocles Foundation long enough for X-Force  to rescue them. He was shot but survived once medical attention was given.
 
His current whereabouts are unknown as are the effects M-Day may have had on his abilities.

Powers

Superhuman strength due to him having a rock like body. It also grants him a degree of invulnerability though not enough to withstand gunfire. 
 

Similarities

He looks similar to the first form taken by Santo Vacaro of the X-Men/ Hellions . However he was created in 1998; a good five years before the series in which Rockslide made his debut. Therefore it is Rockslide who looks like him and not the other way around.