shape of a mountain
嶐 centers on the visual form or outline of a mountain, referring to its shape rather than the mountain itself.
嶐 combines 山 (mountain) with 隆, which likely contributes the sound and the idea of something high or prominent, together suggesting the shape of a mountain.
The mountain 山 sits on top of 隆, which suggests something lofty. Picture the distinctive outline of a mountain peak rising high.
For リュ, imagine a mountain shaped like a giant lyre: lyre -> リュ, and its silhouette forms the mountain's shape.