The Cosmic Monoliths are really easy to kill;
Just have a good resistance agains't Dark and you will GAIN health instead of losing it. Lance can use Officers Hat and Coat and Shadow Blast. That gives him a 130% resistance agains't Dark. Then just use his Bombs and turrets. :)
Tip for beating Akron; Let Nat equip Pope Hat and Obsidian and Lance with Officer Hat and Coat and Shadow Blast. Akron uses attacks with mostly Dark Element and if you should be protected.
Matt should attack the Claws and Worm Things cause he doesn't do that much to Akron. Let Nat and Lance do that. Check which Elements heas eak and strong against each time you fight him they can change.
Stock up with HP and MP gainers cause the battle will be tough.
BTDT is really fun. I LOVE TD:s when you can make a maze of your Towers. Even though this is a really good game Tabletop TD is better. Tabletop is fun and FUNNY!