Bowser Jr.'s mountain castle doesn't feature any extraordinary gimmicks, just a pool of deadly lava and many moving blocks. With the stone blocks often being the only thing that saves you from a fiery death, nothing but good platforming can get you through the castle. At the end of the level, the boss awaits, equipped with some serious artillery. Defeat it to go to the final world!
Once the moving stone block moves in front of you, jump on it and onto the stationary platform. Take out the Koopa and go right. Get on the moving stone block below and jump right when it moves left, which should let you land on another stone block to the right. Jump from this platform to the vertically moving block to your right, then jump up to the stationary column. Drop down and knock the Koopa into its shell and carry it with you. Jump on to the stone block to the right and move to the edge of the stationary platform. Throw the shell off to grab the first Star Coin suspended above the lava.
After that, you must jump on to two moving stone blocks that move under stationary platforms. Time your jumps incorrectly and there will be no safe place to land. On the last stationary platform, leap to the right to land above the second Star Coin. Fall to the moving stone block to the left and let the platform move you into the Star Coin. Back on top of the platform, jump to the stone block at the right and on to the platform with the red Koopa. Wait until the stone block below moves to the right, then jump from the stone block to the ledge on the right, passing the checkpoint.
Move right and use the moving stone blocks to get on to the ceiling blocks. Go right and jump to the floating platform next to the two stone blocks, taking out the red Koopa while you do so. Make a running leap to the right when the top stone block is at its lowest to jump over it, leaving you offscreen. Run to the right to grab the third Star Coin, then return to the platform. Wait until both stone blocks are fully apart before jumping through, or else you risk getting crushed.
Up ahead, you will face a hallway with a ceiling lined with spikes, as well as some moving stone blocks that can push you into the spikes. Cross over these blocks one-by-one when they descend to their lowest point to clear the hallway safely. Enter the door to end up in a mostly-vertical room. Use the moving stone platforms as steps to reach the ledge above you, where the double doors to the boss are located.
Boss: Monty Tank
Monty Moles are surprisingly good engineers employed by the Koopa Troop for underground ambushes and to man cannons. This particular Monty Mole appears to specialize in the latter, getting a powerful and impenetrable tank to use against you. The Monty Mole is invincible while hiding in its tank, but it will often pop its head out to throw Bob-ombs at you, during which you can stomp it to damage it. Every time you stomp the Monty Mole, its tank grows one level taller, making it harder to stomp. The tank can also fire Bullet Bills in multiple directions, an attack that the Monty Mole uses more frequently when low on health. For the final hit, you must even jump off of a Bullet Bill just to reach it at the top. Hit the Monty Tank's driver three times to defeat it, netting you the key to World 8!
- The Star Coin is hovering inches above the lava. Use a Koopa shell to grab it remotely.
- Get on the moving stone platforms to reach the second Star Coin, located in a small alcove.
- On the three block platform next to the colliding stone blocks, make a running leap to jump over the blocks and on to the ceiling. Run right to take the Star Coin.