Search your library for two cards. Put one into your hand and the other into your graveyard. Then shuffle your library.
Is this good at all compared to Dark Petition? Seems like it may have some more combo interactions, since it does fetch a card that you put in your graveyard. Black Lotus and LED (if you can cast the Yawgmoth's Will afterwards) are searchable to make it a comparable cost as Dark Petition.
I think it's too much mana, but maybe it has some synergy with Recoup or other cards you want in your graveyard that I'm not seeing.