So I got stumped with Yggdra Union close to a year ago on the very challenging level 39. Baldus the knight was blocking my path and I could not get past him. He was like an unbreachable wall. Even when I won, if I did not have enough surviving units, his morale would remain unscathed (or close to it). I tried occasionally to get past this level, but I would just give up. I haven't been playing a lot of video games in the past year, and I would just come back to this game on occasion and get frustrated every time.
Then I noticed that two of my cards, Revolution and Mind Change, had been maxed out to level 9999 each. I am not sure how this happened, because I wasn't playing them all that much (I don't think). Compared to the other cards, most of them are only at level 3000 or so at the most. How the heck did I max out these two cards? Did I somehow unlock some secret to the game? I just played Mind Change against Baldus this morning and I totally plowed through him and beat the level easily.