Beast Mode was in the building when the Golden State Warriors beat up on the Cavs on Monday -- celebrating with some of the biggest rappers on the planet. 

Diddy, Snoop and E-40 turned up with the Oakland Raiders running back in the bowels of Oracle Arena.

Marshawn Lynch is a HUUUUGE fan of all things Oakland/Bay Area -- and you know he wasn't gonna miss Game 5.

Guessing he's already got his spot reserved on the float for the victory parade.