Here's the code on the server so it should be working properly (lines I added this morning in green:
if(monsterName == "Del Murder")
{
   battleResults = "You defeated Del Murder and found the key to the tower!";
   document.getElementById("BoardCell" + delCell).className = "barefloor";
   hasKey = true;
   differentEnemiesDefeated++;
}
else if(monsterName == "Dark Del Murder")
{
   battleResults = "You defeated Dark Del Murder!";
   defeatedDarkDel = true;
   differentEnemiesDefeated++;
}