Lock's Quest is a real-time strategy tower defense game developed by 5TH Cell and published by THQ for the Nintendo DS. It was released in 2008. The game combines traditional tower defense gameplay with RPG elements. Players take on the role of Lock, a young boy who stumbles upon an invasion by a mechanical army and uses his engineering skills to defend his village. Throughout the game, players spend time building defenses during the day and defending against attacks at night, while also exploring the world and advancing the story.