Be stoned so Mary Jane is like Medusa,

from Pro Era (Ft. Capital STEEZ, CJ Fly & Joey BADA$$) – Like Water Lyrics 3 on Rap Genius

Meaning

To be stoned is a colloquial for being high (a form of intoxication), he is high from Mary Jane which is another colloquial for the drug Canibus. (Marijuana).

However, in this line Mary Jane is both a reference to Marijuana and its a fictious character that get’s *stoned by Medusa.

Stoned as in high
Stoned as in stoned from Medusa, in greek mythology looking upon Medusa turned your body into stone

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