After many, many more attempts, I finally managed to save Meden. I’d tried every combination of Patapon armies to do it, but in the end my standard Tate/Yari/Yumi setup was enough.
Then it was off to fight a harder version of the crab boss I killed earlier, who dropped the ability to create Megapons. I haven’t made any yet, though. I did, however, come up against some (sort of) in the next mission – where I had to kill off Gong once and for all. He had a huge army of Zigatons behind him, and took a few attempts to defeat. Once I did, I gained his scythe!
After that, it would appear that the Zigatons all sold their souls to demons, and the next mission required me to take out a tank, an evil Zigaton-demon called Spiderton, and a huge… thing. That was pretty easy though.
What was not easy, however, was the giant castle made of plants and eyes that I had to defeat on the next mission. I’m still trying to figure out the best combination of Patapons to take into battle…