This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
觹 combines 角 (horn) with 雋, but the exact historical development and original meaning are uncertain. It may have originally referred to a horn tool or vessel, but this is speculative.
With 角 (horn) on the left and a complex right side, 觹 looks like an ancient horn implement. Since no clear meaning is known, picture it as a mysterious horn-shaped tool whose use has been forgotten.
For ケイ, imagine a horn-shaped key unlocking an ancient chest: key -> ケイ, and the horn tool 觹 is the key.