noun
principal object of worship; main image; idol
Buddhist term for the central statue or image enshrined in a temple, usually a buddha or bodhisattva. Used in formal or religious contexts.
このお寺の御本尊は阿弥陀如来です。
The principal object of worship at this temple is Amida Nyorai.
noun
the man himself; the central figure
Jocular, humorous use referring to the key person in a situation, as if they were the main object of worship. Often used in casual conversation or light-hearted writing.
やっと御本尊が登場した。
At last, the man himself appeared.
本尊 is the base word meaning 'principal image' or 'object of worship' without the honorific prefix. 御本尊 adds politeness and is more common in respectful reference.
From 御 (honorific prefix) + 本尊 (principal object of worship). The jocular sense is a metaphorical extension.