Though it is never answered in the movie what is in the ব্রিফকেস (just knowing that what is in there is valuable and emits some sort of golden glow), there are several theories. One is that the ব্রিফকেস contains the diamonds from "Reservoir Dogs". Another is that the ব্রিফকেস contains Marcellus Wallace's soul. I personally think that Quentin Tarantino left the idea of what's in the ব্রিফকেস for the viewer to guess.
The whole idea behind the suitcase is that it is the most valuable thing that the viewer can think of. Whether আপনি want to think it is full of money অথবা the Koh-I-Noor diamond, it's your choice.
