LeBron James will never be in the dark again ... 'cause the LA Lakers superstar just copped a SICK new diamond pendant -- and it LIGHTS UP!!! TMZ Sports has learned ... Bron is the proud new owner of a "Lion Gatekeeper" pendant ... complete with 130 grams of 14k gold, encrusted with 35 carats of VS1 diamonds. We're told LBJ hit up celeb jeweler Iceman Nick when he was in Houston to play the Rockets ... and the dude pulled out all the stops to come up with a pendant fit for a king. Of course, LeBron's always been a fan of using lions in his brand ... and Nike once even had a "Heart of a Lion" campaign starring James. (full story)