I am currently trying to get this otter to level 30! As of right now, he's still on level 15 and I'm nowhere close to 16 yet. The way I'm getting him there is by playing The Hive over and over. Each time I play that adventure, I choose the Fire Drum as a prize (whether in hard mode or not) and I'm currently filling up an entire Volcano Den with Fire Drums. Who knows how many I'll end up with!