This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
魌 combines the demon radical 鬼 with the phonetic component 其. The exact historical development and original meaning are uncertain.
The kanji has no clear meaning, but visually it shows a demon 鬼 enclosing a winnowing basket 其. Imagine a demon hiding behind a basket, its purpose unknown.
For キ, picture a key unlocking the demon's basket: key -> キ, and the demon 鬼 inside 其 is revealed.