I suspect my opponent/teammate is cheating. How secure is BattleForge?
Since it is an online game, each of the player’s games have to match each other. If an opponent breaks the rules somehow by hacking his client, the change will be an irregularity. It will create a desyncronization error with the other players and end the game. Also, you can always look up replays. They are auto-saved after each game. Exam closely what the other player did, and learn from it. Chances are he used a card or tactic you are unfamiliar with. If you are still convinced that he did something wrong, ask about it on the forums. There are many experts who know fully what is possible and what is not.