The Glass Is Half Empty!

The Glass Is Half Empty! (Multi Moon title: The Glass Is Half Full!) is the sole story mission of the Seaside Kingdom in Super Mario Odyssey. The mission's objective is to stop Mollusque-Lanceur from stealing all of the Sparkle Water from the Glass Tower by hitting four switches that activate fountains, which each fire a cork at Lanceur.

Layout
The mission begins at the Odyssey, with Mollusque-Lanceur draining all the Sparkle Water in the Glass Tower with a drinking straw. To stop the thief, Mario must hit four Ground-Pound Switches scattered throughout the kingdom, each requiring a nearby Power Moon to be collected to be unlocked. The four switches are found on top of a tall rock pillar near the Beach House that requires capturing a Gushen to access, on top of the Lighthouse, under lava-coated water on Hot Spring Island, and at the ledge of Rolling Canyon.

Each switch causes a fountain to start flowing, causing the cork that capped off each to fly off, hitting Mollusque-Lanceur. Each time he is hit, Lanceur gets progressively angrier and starts to fire Spiked Shells into the water below. Once all four switches are hit, Lanceur is knocked off the Glass Tower, starting the boss fight. Uniquely, this boss fight takes place across the entire kingdom. To damage Mollusque-Lanceur, Mario must capture a Gushen and spray the top of Lanceur's head with water.

Once Lanceur is sprayed enough times, he explodes, causing Mario to be launched to the top of the Glass Tower, landing on a cork floating on top of the water. There, Mario can collect the Multi Moon Lanceur had, ending the mission.

Smaller objectives

 * The Glass Is Half Full!: The mission's name (on the brochure screen and in the introductory cutscene if Mario leaves then returns to the kingdom) changes to this objective after initiating the boss fight with Mollusque-Lanceur. The goal is to defeat Lanceur and obtain the Multi Moon from him.

Power Moons obtained

 * The Stone Pillar Seal: Found on top of the rock pillar south-west of the Glass Tower. Collecting it unlocks the switch that uncorks the south-western fountain.
 * The Lighthouse Seal: Found on top of the Lighthouse, which can be reached through the underwater tunnel north of it. Collecting it unlocks the switch that uncorks the north-western fountain.
 * The Hot Spring Seal: Found at the bottom of the hot spring coated with lava, which can be cleared away with a Gushen. Collecting it unlocks the switch that uncorks the north-eastern fountain.
 * The Seal Above the Canyon: Found at the end of the Rolling Canyon path with the Spiked Shells. Collecting it unlocks the switch that uncorks the south-eastern fountain.
 * The Glass Is Half Full! (Multi Moon): Obtained after defeating Mollusque-Lanceur.

Enemies

 * Goombas
 * Micro Goombas
 * Cheep Cheeps
 * Gushens
 * Maw-Rays
 * Komboos
 * Spinies
 * Spiked Shells
 * Moonsnakes
 * Mollusque-Lanceur (boss)