In Castlevania: Harmony of Despair for the Xbox 360, there is a hidden item in each chapter that will boost your end score when you collect them.
Vic Viper is hidden in Chapter 5. In the upper right hand corner of the stage, go down the hole to the right of the blue chest and fall to a platform. Go right as far as you can go and when you hit the wall, hold Up to make it appear.
There are six hidden items to collect, so check out my guide to find the other hidden items in Castlevania: Harmony of Despair.
