They were in Armageddon, and were listed as having deployed 2 Brotherhoods (the White Scars version of a company). This from Wikipedia:
Storm Lords
A Second Founding chapter of the White Scars. Their power armour is painted half-white half-red, with yellow helmets. The Chapter's symbol is a skull superimposed over three lightning bolts. The Storm Lords participated in the effort to free the Crimson Fists' homeworld from the Orks.