Wario Land 3: Part 49: Desert Ruins (Blue Chest)

In this part of the Desert Ruins, you must play at night. First, go through the Moon gate and use a Super Ground Pound on the solid purple blocks in the next room to access a new path and doorway. Then, using Vampire/Bat Wario, fly up to the blue key while avoiding the shining lights that will revert Wario to normal. Ground pound through the larger blocks to reach another doorway. Next, use Bouncy Wario to bounce up to a switch block, activate it, and release the block platforms in the bat room. Proceed through the doorway that was previously blocked, which leads to a boss battle against Yellow Belly. Avoid his spears, or he will get puffy and leave the arena. Ground pound his head and the springs that emerge from him to make him bloat; keep doing this until he pops, and the blue chest is yours. The blue chest contains the bottom half of the Sun Medallion, and you must find the top half next.