Can you be fined more than your deposit for canceling a hall?

if you cancel at a banquet hall can they fine you more than your deposit. I want to cancel at a hall and they say they will fine me 80% of the total cost. But so far i have only paid a deposit. The contract they drew up was sketchy at best, and according to them it states you lose that 80%. Can they actually do that, or will i only lost my deposit. I have heard terrible things about this place and want out if possible.