This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
魿 combines 魚 (fish) with 令, which likely serves as a phonetic component. The exact historical development is uncertain.
The left side is 魚 (fish) and the right side is 令. Since the meaning is unclear, picture a fish with a commanding presence, as if giving orders, but remember its meaning is uncertain.
For レイ, imagine a ray (レイ) of light shining on the fish, making its scales glisten. The ray sound cues レイ.