Loeb's $14.5 billion hedge fund Third Point currently owns a 9.6 percent stake in Sotheby's and started a proxy contest earlier this year, putting Loeb and two other people forward as directors. Since the middle of last year, Loeb and Third Point have been pushing the company to overhaul its financial strategy, return capital to investors and improve its position in the modern art market.
Read MoreSotheby's made a strong case to reject Loeb's slate: source
To some observers, the battle is being drawn along the same lines as the 2012 battle for Yahoo, in which Loeb played an instrumental role in pushing out Scott Thompson as chief executive and hand-picking Marissa Meyer to run the company. The two sides negotiated a settlement and Loeb joined Yahoo's board.
Sotheby's share price has fallen 21.33 percent since October 2013. The company in October adopted a poison pill to prevent activist investors from owning more than 10 percent, two days after Loeb raised his stake in the company. Third Point has filed suit in Delaware Chancery Court to try and force Sotheby's to withdraw the poison pill. The next hearing is scheduled for April 26.
Loeb said Sotheby's was disingenuous in criticizing his exit from Yahoo last year. Loeb said Yahoo's share price climbed more than 85 percent during the time he and two other directors close to Third Point served on the board.
Read More Loeb: 'Failed' board dragging down Sotheby's stock
He also said that Sotheby's made "false statements" about his experience in the art world. He said that as a prominent collector he has loaned some of his personal collection to museums like the Museum of Modern Art in New York.
Sotheby's annual meeting will take place on May 6, and before then Loeb and Sotheby's will both try to persuade investors to their side. Proxy voting advisory firm ISS is expected to make a recommendation on which slate to pick in the coming days.