The West Crater

The West Crater is a level located in the west side of the Music Box World in Wario Land 3. It's only accessible after the volcano erupts when Wario uses the three conch artificats. It is unlocked along with The Colossal Hole.

The treasure hunting takes place inside the volcano. This level has Fire Robotas, Hammer-bot and has flames that blocks the way to the upper-left which can be pulled out using the Fire Drencher found in Above the Clouds.

Grey Chest : Blue Snake Eye (left)
To get the gray key, Wario has to go to the bottom of the level and use the Fire Wario form to break the blocks to the right and manage to get the key.

Then, he has to come back to the upper area and make his way to a door by breaking walls. Then he has to use the Ball o' String Wario to break the string blocks and finally open the chest to get the left eye of the blue snake.