Mollusque-Lanceur Battle

Walkthrough: After breaking all four seals, head to the center of Bubblaine to take on Mollusque-Lanceur. The battle will begin with Mollusque-Lanceur throwing more exploding shells at you. Dodge the best you can, capturing one of the Gushen as you do to help in this fight. Mollusque-Lanceur's head will be covered in lava, so use the Gushen as you did earlier to clear the lava off the top of his head. After getting rid of all of the magma on his head, his head will become vulnerable for an attack. Quickly hover over the monster, and then leave the Gushen and jump straight on his head.

After landing a key blow to his head, Mollusque-Lanceur will start backing away from you, still launching spiked shells has he does. Capture the Gushen once again and keep pace with the creature. Do the same as before, using its water cannon to hover over the head of Mollusque-Lanceur. As you do, quickly leave the Gushen and land another jump to his head as Mario. The final phase will be more of the same, except for the fact that the monster will be even faster and shooting a variety of exploding shells. Do as before and land the final blow to his head. After he is defeated, you will obtain a Multi Moon.

Winning will conclude you objectives in Seaside Kingdom. If you still a few more Power Moons in order to leave, start exploring the islands to find the necessary number of which you need. After having enough Power Moons to proceed, you will continue to Snow Kingdom if you chose to complete Seaside Kingdom first. If both Snow Kingdom and Seaside Kingdom are complete, Mario and Cappy will continue to Luncheon Kingdom.