This trophy is obtained for completion of the fifth main story mission and is thus an unmissable part of the progression through the game.
**Minor Mission Spoilers Follow**
Upon checking in at the adventurer's guild after finishing the fourth mission you will be directed to search for Samuel (Adventurer's Guildmaster) in town. Locate him praying in Chapel (you have to select 'Pray'). He directs you to the 'Castle of the Dead: Catacombs' (fifth dungeon level) to search for missing village girls. At the end of the dungeon you will fight multiple vampires as the boss. After finishing the dungeon, Report to the adventurer's guild to obtain your gold reward and also this trophy.