Rystil Arden said:They might not ruin the other players' time necessarily, if they save it for when the chips are down though. The vampire character can be open about it to the other characters "Look guys. I'm a vampire. I generally don't plan on creating an army of spawn, but if we ever come across something that is too hard to beat, I'm willing to do it, and we should be able to completely slaughter the opposition that way as 1000s of vampire spawn back us up."
Except they can't get thousands of vampire spawn to back them up. "At any given time a vampire may have enslaved spawn totaling no more than twice its own Hit Dice; any spawn it creates that would exceed this limit are created as free-willed vampires or vampire spawn." For an ECL 13 vampire, that means exactly two enslaved vampire spawn.
And anyway, we weren't talking about the party running into a monster that was too hard to beat. We were talking about the vampire using his create spawn ability to create havoc in the city after being found out and having clerics from the local temples come after him. That would ruin the cool urban, social/political campaign we were discussing. After all, there's not much point in trying to foil Lord Hilgorson's plot to take over the city council when half the city has been turned into vampire spawn or wights and is busy slaughtering the other half.