Be Darius and spend 1500 xp?  It's actually on my list of things to do.<br/><br/>It's a Space Marine elite advance, one of the many augments that full fledged Space Marines get, no doubt.  It's unlikely that any of the other players could get it that way, though.  I'd bet it'd be available for the price of a soul... should anyone happen to fall to Chaos, and have a particularly valuable soul, however.