Orcs Must Die! Unchained will be a PC-exclusive free-to-play “Fortress Siege” multiplayer game when it’s released in late 2014, developer Robot Entertainment has announced.

Orcs Must Die! and Orcs Must Die! 2 offered a more action-oriented spin on the tower defense genre, asking you to defend your castle against hordes of orcs by setting traps and fighting them yourself from a third-person perspective.

“After the first game, fans told us they wanted cooperative gameplay, and we were thrilled to deliver it in Orcs Must Die! 2,” Robot Entertainment CEO Patrick Hudson said. “After the sequel, we heard the cry for competitive gameplay. Orcs Must Die! Unchained is an answer to that and much more. It’s a realization of Robot’s ambition for what the franchise could ultimately become.”

Orcs Must Die! Unchained keeps the basic mechanics, but structures them around a head-to-head multiplayer game where one team defends a fortress, and the other attacks it. Players will be able to choose between dozens of unique heroes, including War Mage and Sorceress from the previous games, and new heroes like Blackpaw, Midnight, Stinkeye, and Bloodspike. As you play, you’ll add more heroes, weapons, traps, and minions to your arsenal.

While Orcs Must Die! Unchained will be free-to-play when it’s released, you can start playing the Alpha instantly if you buy The Master Founder’s Pack for $150. It will also get you five heroes to play with, 200 in-game gold, one Alpha code to give to a friend, five unlock codes for the previous Orcs Must Die! games, access to the developer forum, and more. The $60 War Mage Founder’s Pack will put you at the front of the line for Alpha testing, and the $20 Apprentice Founder’s Pack will get you priority access to the closed Beta.

You can find the full list of rewards for each Founder’s Pack on the game’s official website. If you’re at PAX East, you can also check out a playable version of Orcs Must Die! Unchained at booth 1124.