How Hermitage Capital, Ziff Brothers And The Clinton Global Initiative Prompted The Trump Jr. Meeting

When Trump Jr. took his now-infamous meeting with Russian lawyer Natalia Veselnitskaya he was promised "official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father." That said, Trump Jr. has since described Veselnitskaya's 'damaging information' as nothing more than "inane nonsense."
So what "information" was Veselnitskaya peddling that could be used as a political weapon in the 2016 presidential election?