Thought you knew all about the many tentacles the Koch brothers’ have around American politics? Politico’s Jim VandeHei and Mike Allen have the story of a heretofore unknown pot of cash that they and other deep-pocketed donors spread around in 2012…

An Arlington, Va.-based conservative group, whose existence until now was unknown to almost everyone in politics, raised and spent $250 million in 2012 to shape political and policy debate nationwide.

The group, Freedom Partners, and its president, Marc Short, serve as an outlet for the ideas and funds of the mysterious Koch brothers, cutting checks as large as $63 million to groups promoting conservative causes, according to an IRS document to be filed shortly.

The 38-page IRS filing amounts to the Rosetta Stone of the vast web of conservative groups — some prominent, some obscure — that spend time, money and resources to influence public debate, especially over Obamacare.

The group has about 200 donors, each paying at least $100,000 in annual dues. It raised $256 million in the year after its creation in November 2011, the document shows. And it made grants of $236 million — meaning a totally unknown group was the largest sugar daddy for conservative groups in the last election, second in total spending only to Karl Rove’s American Crossroads and Crossroads GPS, which together spent about $300 million.