I didn't rescue the Vampires, because I didn't know the map. I used the sight of evil spell, and saw many enemies, the ones in the building behind locked doors I discovered later. But I didn't know they where behind locked doors, so I waited with digging to the water, until I had enough trained skeletons to survive some large fight. The only thing I saw was that the enemy Keeper had 40 creatures, me only 15, and that the enemy Keeper would attack the large hero building in the south, because I saw him using Call to Arms and had a look with the sight.
When I dug to the water, I discovered that the hero buildings where locked. I didn't know what was behind my walls, and dug by taking care not to open the water, that I checked with the sight spell. After I researched the temple, I opened to the water, and discovered it was easy there, and had to hurry, because the enemy Keeper was already digging some Gold.
This Keeper came very close to my dungeon, would claim his tiles from the path I had dug to the water. He had a lot more creatures than me, so I had a hard time defeating him.