Private-equity firm Silver Lake is asking a judge to declare that activist investor Carl Icahn and a group of hedge funds illegally colluded in attempts to fight the $13 billion acquisition of talent agency Endeavor.

There are billions of dollars at stake and now a legal debate that could upend the entire merger arbitrage industry.

Silver Lake, Endeavor, Icahn and shareholders have been locked in legal battles since the deal closed early last year, with the shareholders arguing the buyout underpriced by billions of dollars the owner of agencies WME and IMG and headed by Hollywood superagent Ari Emanuel.

At the center of the dispute has been Endeavor's majority stake in TKO Group Holdings, the owner of UFC (Ultimate Fighting Championship) and WWE (World Wrestling Entertainment). Shares of TKO rallied between the time Silver Lake announced the Endeavor take-private deal in April 2024 and its closing in March 2025.

That is when investors started buying into Endeavor.

Silver Lake already controlled the votes in Endeavor before the deal, allowing it to skip a shareholder vote and stick by the price it said was a 57% premium. Icahn and others have since sued, saying the deal and management undercut public shareholders for their own gains.

On Monday, the company launched a new broadside that would have the investors' shares thrown out of appraisal proceedings, which ask the Delaware Court of Chancery to declare the fair value of the company.

In essence, Endeavor and Silver Lake argue the investors are interlopers who shouldn't have a voice in the appraisal fight because they bought after the deal was agreed.

A ruling on that could be a landmark decision on the rights of these arbitrageurs, an industry that buys up shares in announced deals. These funds often pocket profits when the deals close from small technical price changes and sometimes fight for higher payouts.

Appraisals are a risky move because a judge will determine the ultimate price, which could give the investors more or less than the agreed deal. More than 70% of the public shares of Endeavor have filed for appraisal rights in the biggest such case in Delaware history.

Silver Lake, which continues to defend the $27.50 per share price, says most of the shares involved were purchased long after the deal and were only bought to wage an appraisal fight, which it argues isn't the intent of the law.

"The appraisal statute never was intended to allow opportunistic funds, like Defendants here, to acquire shares after a merger was announced and pursue windfall profits," the filing said.

The firm also alleges the actions of Icahn and two of his allies, Troluce Capital Advisors and Pentwater Capital, who all hold significant stakes, amounts to illegal collusion. The firm alleged the three investors failed to file proper disclosure forms, allowing them to acquire even more shares, and partner together in a legal strategy. Troluce's co-founder, Jonathan Christodoro, was a top deputy at Icahn's firm until leaving in 2017.

Icahn's firm isn't part of the appraisal case, but is leading a separate suit arguing the management failed its duty to shareholders.

"It is clear that certain of the Defendants engaged in an unlawfully coordinated and anticompetitive-and unlawfully undisclosed-scheme to acquire Endeavor shares for the common goal of pursuing a litigation arbitrage strategy," Silver Lake's filing said.

Representatives of Icahn, Pentwater and Troluce didn't immediately respond to requests for comment.

Silver Lake and Icahn already have a tortured history.

In 2013, Silver Lake teamed up with Michael Dell to take his computer company private for $25 billion. Icahn jumped into that deal with other big investors and waged one of the most-heated deal fights in history, arguing the price was undervalued. After the buyers bumped the price, the shareholders approved the deal over Icahn's objections.

Three years later, a Delaware judge in an arbitration case like the one at issue in Endeavor sided with several investors and ruled Silver Lake and Dell underpaid.