In this paper, to handle the problem of the quick evolution of cyber-security attacks, we developed the iMonsters board game and proposed the attack and defense knowledge self-evolving algorithm. Three versions of the iMonsters were launched in 2013, 2017, and 2019, respectively. Accordingly, the cyber-security ontology can be refined by the ontology fusion-or-splitting procedure for the newly collected cyber-security incidents, as well as the roles and rules of the iMonsters can be refined by the gaming portfolio mining procedure for the collected portfolio. Furthermore, we conducted game-based learning (GBL), a quasi-experiment of pre/post-testing, and concept map testing using the iMonsters board game in a children's summer camp. The experimental results indicate that the students can acquire up-to-date cyber-security knowledge with the iMonsters better than students who learn in a traditional classroom setting, and the students' satisfaction with acquiring cyber-security knowledge with the instructional design of the iMonsters is better compared with learning in a traditional classroom setting. Satisfaction with the new version has continuously increased. Besides, the results of the in-depth interviews show that the new version was easier to learn. Thus, we may conclude that using the self-evolving iMonsters can improve learning effectiveness and participation in GBL.