Melty Molten Galaxy is accessible from the Garden observation dome. You need 52 Stars to enter.
Star 1: The Sinking Lava Spire[edit]
Welcome to Melty Molten Galaxy! When you first land, beware the lava pools that surround you. Also beware the fire clouds that will try to chase you: spin while by them to make them fall, and then run into them to defeat them and get a coin. Watch out also for the holes in the ground that shoot hot air, they will make you lose a third of your life circle. Spin to get the treasures encase in the glass and make your way around the lava pools and to the largest lava lake ahead of you and to the right. Jump across the gap, but make sure the shooting lava pillars don't hit you! Jump onto the purple platform, but beware because it tilts. Run across it and grab the two coins while jumping to the blue platform. From here, jump to the long green platform, but watch out because both of those sink if you stand on them for too long.
Now off the sinking green platforms of doom, you find yourself back on the rocky terrain like the area where you first landed. To your left are some Star Bits encased in glass. Climb the steps but beware the fire cloud. Cross the line of hot air geysers and wall jump onto the stone button. Ground pound. Wall jump once again to the top of the mountain. Not much is up here, unless you need two coins which are at the top of the wall and stairs on the left of the mountain. Use the Sling Star, but don't shake on the second Sling Star. You will slide down the volcano onto a platform with two coins. Collect them and use the Sling Star there. Repeat the above steps to once again get to the Sling Star you just fell through. Shake this time and you'll be slung to a Launch Star over a volcano. Again, don't shake. Fall into the volcano, and ground pound the red button. Star Bits will appear collect them all with your remote but stay on the red button because the lava will rise. Use the Sling Star to get out of there. Use the Launch Star and enjoy the pretty view. Don't forget to collect the Star Bits circling you as you fly.
Shake on the Sling Star to avoid falling onto the lava planet. You may now jump between the glass planets. There is a Hungry Luma that leads to the Hidden Star in this galaxy (Burning Tide): if you want to do that, read elsewhere, otherwise ignore it. Jump to the uppermost planet and use the Pull Stars to navigate the fiery planets. Beware because some shoot fire balls to each other. Use the groupings of three Pull Stars and don't try to skip parts because there is a 6-Life Mushroom. Use the final line of Pull Stars to get yourself to the Launch Star and launch away. You'll fall into another Launch Star above the lava, so shake as quickly as possible here.
You will land on a spire that is rising above the lava, hence the star's name. It will start sinking into the lava, so navigate through it as quickly as possible. You can collect the items inside the item crystals if you want, but you have to do it quickly; likewise the 1-Up mushroom near the top of the spire. After navigating through enemies, boulders, and a switch, you'll see the power star embedded inside an item crystal. If you want, get the items inside the crystals around the power star, then spin attack the power star crystal twice. After that, go and claim your power star!
Star 2: Through the Meteor Storm[edit]
You must first get past all of the meteors until you get to the two unlit torches. Attract the flying fire critter towards you, but be careful not to touch him. Walk towards the torches and when the fire critter touches them, they catch fire. A Launch Star will appear. Take it to an octagonal planet with Thwomps. Go around it, avoiding Thwomps, meteors, and the black hole in the middle. Launch to the next planet.
(next part coming soon)
Star 3: Fiery Dino Piranha[edit]
You start in the same area as the previous missions. Go across the small sinking platforms and up to a pipe. Take it to land on a saucer with a Sling Star. Take it to an area where you need to defeat all the enemies to reveal the Launch Star. Land on a rotating planet with fireballs circling it. Avoid the fireballs and lava, then take the Launch Star at the end to a 2-D section. Here, you need to find the five star chips to make a Launch Star. There is a Life Mushroom, if you need it. Launch to a section with lots of sinking platforms. Use the Sling Stars to go between them. At the end, you will reach a Luma Shop to buy either a 1-Up Mushroom or a Life Mushroom for 30 Star Bits. The Life Mushroom might be useful if you need help during the upcoming boss fight.
Boss Fight - Fiery Dino Piranha. This boss fight is similar to Star 1 in the Good Egg Galaxy. His tail switches between fiery and cooled down, and you need to spin attack it when it is cooled down. The boss also spits fireballs after a few hits. He runs faster than the original Dino Piranha, and he can sometimes surprise attack you by charging in your direction.
If you need to replenish your health, there is a coin trapped in crystal, and you can fire Star Bits at two flowers to receive coins. It is also helpful to break the crystals that have Star Bits in them beforehand, so that they will be out of your way when you fight the boss.
Star 4 (Daredevil Comet): Lava Spire Daredevil Run[edit]
Same as Star 1, one with just one life point.
Star 5 (Purple Comet): Red-Hot Purple Coins[edit]
100 Purple Coins, no time limit.
Star 6 (Hidden): Burning Tide[edit]
Enter Star 1. Feed the Hungry Luma 80 Star Bits. Take the launch onto a new planet with rising and falling lava. The white parts indicate safe zones that the lava won't reach, so use that information to help you. Find the five Silver Stars while avoiding the lava, Fire Bars, and other hazards. The Power Star doesn't appear in a safe zone, so be careful when getting it. If you are close enough, you can risk long-jumping to it.