Mt. Itoi (also written as Mount Itoi or HOLY LOLY MOUNTAIN in the Japanese Version) is one of the final areas in Mother. It is notorious for being an extremely difficult area, and when Shigesato Itoi was asked of this, he said that the game was so close to completion he rushed everything and didn't have time to test the difficulty.[1] The seventh and eighth melodies are both located here. The Japanese Manuel states that it is considered a sacred place, and that few people ever travel up it.
The mountain consists of a large cave at its base, with a plateau at the end of the cave which contains a small rest house. Higher up on the mountain is a large lake with a central whirlpool.
Eve is found in the central lake, in a lab located underneath the whirlpool. Lloyd is required to fix a boat on the eastern dock in order to navigate the lake. Higher up on the mountain, Eve dies at the hands of R7038XX, bearing the seventh melody. In the English prototype and Mother 1+2 versions of the game, the XX Stone at the mountain's peak bears the 8th melody, while in the original Japanese version, Queen Mary instead remembers the final melody on her own. Nearing the peak, Ninten's party is required to climb an increasing number of vines, as the mountain transitions from a mostly-flat section to a rocky outcropping.
Mt. Itoi, as it appeared in the commercial for Mother.
References
↑"What I get most is, “I’m at Mt. Itoi now, help!” That place is just crazy. When we got to fine-tuning there, I was like, “Whatever!”" --Shigesato Itoi (footage)