Here's some ideas of mine:

Craterock Reactor Core: On the planet Craterock, the home of the race of yellow lizards recruited by Devan Shell, the turtles have changed the beautiful green planet into a giant turtle military base. The base is powered by a giant reactor core deep inside the planet. Destroy the core to shut the base down. The core is a massive white-hot machine that spews dozens of flaming embers in all directions. The machine is only vulnerable when it is cooled far below operating temperature. Hit it with the freezethrower and then fire electro-blaster shots at it before the freeze effect wears out. You will need to do this many times to destroy the reactor core.

Uberturtle: The Uberturtle is a gigantic mutant turtle that was developed by Devan Shell to be the ultimate soldier. The Uberturtle is pretty basic. He will run around trying to stomp you. Just avoid his stomp and fill him full of holes until he expires.