Kellan Lutz has been tapped to join the cast of Relativity Media’s Greek mythology clash “War of the Gods” opposite Henry Cavill, Mickey Rourke and Freida Pinto.

Lutz (“Twilight”) has been cast as Poseidon, lord of the sea. Tarsem Singh is directing, with production set to start in April.

Story follows Theseus, a young warrior who leads his men into battle with the immortal Greek gods.

“War of the Gods” will be produced by Gianni Nunnari of Hollywood Gang Prods., Mark Canton of Atmosphere Entertainment and Relativity topper Ryan Kavanaugh. Nunnari and Canton partnered on 2007’s “300,” producing the sword-and-sandals saga for Warner Bros.

Universal will distribute. Relativity’s Tucker Tooley and Craig Flores of Hollywood Gang are exec producing.

Jason Keller penned the most recent draft of the script. An earlier version was written by Christian Gudegast; producers began development in 2008 after buying a spec from Charley and Vlas Parlapanides.

Lutz has portrayed the Emmet Cullen character in the first two “Twilight” pics. Other credits include the upcoming “Nightmare on Elm Street” and police drama-comedy “Meskada.”