dim, obscure
朦 centers on a lack of visual clarity: something dim, hazy, or obscured, as if seen through fog or in faint light.
朦 combines 月 (moon, flesh) with 蒙, which likely contributes the sound and the idea of covering or dimness. The moon component may suggest faint moonlight, fitting the meaning of dimness.
The moon 月 on the left is veiled by the complex right side 蒙, like moonlight struggling through thick clouds. Everything looks dim and obscure.
For モウ, imagine a dim, foggy moor where the moon is barely visible: moor -> モウ, and the scene is as obscure as the kanji's meaning.