Stone was the favoured pupil of Stick, the blind former mentor of costumed crime-fighter Daredevil and Elektra Natchios. He is a member of the Chaste and is a highly trained martial artist and assissts his sensei against the Hand. Like the other members of the Chaste, Stone is deeply advanced in the art of chi-manipulation. An offshoot of this is his ability to render himself invulnerable to physical harm - but only if he sees it coming. Wikipedia
The definitive Wikipedia entry for Stone. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Stone_%28Marvel_Comics%29