In Guardians of the Galaxy, Peter Quill attempts to sell the Orb of Morag to The Broker on Xandar. This deal falls through when Peter reveals that Ronan's after the Orb. The Broker then refuses to buy the Orb. We later see both The Collector and Thanos are after the Orb, but it doesn't seem like the Broker is working for either of them. The Broker refused to reveal who he was buying the Orb for, but it implies some 3rd person is seeking the Orb.
Who was the Broker buying the Orb for?