A Malaysian energy company has accused a prominent U.K. litigation funder of ‘wilful negligence’ in a case that centres on a group of individuals who claim to have “incurred significant damage” due to what the company described as a “rogue” $15 billion arbitration award.

Petronas Azerbaijan—owned by the Malaysian government—is seeking to subpoena Therium Capital Management in connection with a dispute brought by a group of Filipino citizens against Malaysia. The claimants, who say they are the descendants of the last Sultan of Sulu, are seeking compensation from Malaysia for their ancestors’ land under a 19th-century forever lease agreement, according to a court filing.