Mountain trolls, stone golems, and fire breathing dragons are invading mobile devices. The hybrid tower defense title CastleStorm is coming to Android and iOS devices.

CastleStorm: Free To Siege is a free-to-play mobile game. The four nations from the PC/console original will return with their own troop classes, weapons, and spells. Once the game is released, it will feature eight playable heroes. CastleStorm: Free To Siege will also contain new spells for its mobile versions of the game.

Android users can get their hands on the game early by signing up for a private beta now through the game’s Google Groups but space is limited. CastleStorm: Free To Siege will be available this spring.