Roscón de Reyes is a type of cake traditionally eaten on the day of the Epiphany (6 Jan).

One of the traditions of the cake is that there is a prize (usually a small ceramic figure) and an uncooked bean (meaning you are the one to pay for it, but not really done anymore) hidden inside. A few places put big prizes (there's a place in La Bañeza that does 50k€ IIRC) in their roscones as a promotion and looks like IB is doing similar.