The legal battle over one of the biggest brands in the video game industry has leveled up.

Thirty-eight former and current employees of Infinity Ward — the Encino-based development studio that makes the Call of Duty: Modern Warfare video games for Activision Blizzard Inc. — have sued Activision, claiming they are owed between $75 million and $125 million in unpaid royalties.

Last month former Infinity Ward heads Jason West and Vince Zampella were fired by Activision and filed a $36-million suit against the Santa Monica publisher.

Many Infinity Ward employees have quit recently, including 21 plaintiffs in the new suit. Some joined West and Zampella's new firm, Respawn Entertainment.

The suit filed Tuesday in Los Angeles Superior Courtalleges that the publisher has withheld royalty payments for Modern Warfare 2 in order to keep employees from leaving before finishing work on Modern Warfare 3, planned for release in 2011.

An Activision spokesman said, "Activision retains the discretion to determine the amount and the schedule of bonus payments for [Modern Warfare 2] and has acted consistent with its rights and the law at all times."

ben.fritz@latimes.com

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