You need 55 gems to unlock this level. I have 78.
Toadette finds herself in a cave that's different from the one Captain Toad met Draggadon in. Walk around and Draggadon will appear, with a bump on his head from tangling with Captain Toad. Drop down under the platform you start on and you'll find a hole to the first gem and some coins. There are several gears in the level you can spin. These will spin some shields around so you can protect yourself from Draggadon's flames or progress through the level. Past the first gear is another gear that will spin a bridge into alignment. It has a plant with multiple coins. Use the fan to go up, then drop down towards the wall. There's a plant there with the second gem. The lava starts rising. There's a gear to spin that controls two shields. You'll have to leave yourself open to attack with the first shield in order to pass the second shield. Fireballs will start raining down and leaving lava pools, so be careful. Just up ahead is a fan that is level with the ground. Move it out of the way and drop down to find some coins and the third gem. Walk to the right to find a ladder to get out of that area. Up ahead is a shielded elevator. Spin the gear to make it rise, but do not spin it once you reach the top. Use the fan to cross the lava, spin the gear, and cross the lava on the other side with another fan. This will take you to the ladder to the Star, which will fall and hit Draggadon on the head again. Get the Star on his nose.
Special Challenge: Do not take damage.
After you get the Star, you can control Draggadon. Use the directional pad to change height, then press (A) to breathe fire, which turns brick blocks into coins. After a while, you'll go to the next level.