On mission 6 or Return To Frankenstein's Castle there are to life replenishers, to get the first one after entering the castle's broken gates kill all the werewolves and then stand in the centre of the area. Then hold R1 and walk aroung near the centre, if you are in the right position your icon should glow red if it does then press circle. You won't go anywhere but a life replenisher will drop down. To get the secong one you have to stand right next to the egg pedistal in the same area, keep walking around while holding R1 until the grapple icon glows red, when it does shoot the hook and you will go up onto a thin ledge. Walk along the edge until you reach a wooden door, shoot it with the shotgun and there will be a life replenisher in it.