This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 盠 is uncertain. It visually combines 彖 and 皿, but the original semantic and phonetic roles of these components are unclear.
The top 彖 looks like a stylized animal, and the bottom 皿 is a dish. Picture an ancient ritual vessel shaped like an animal, but its exact purpose is lost to time.
For レイ, imagine a ray of light shining on an old dish: ray -> レイ, illuminating the mysterious vessel.