My wild guess is that not all created dwarven vampires were involved in Undurkon's traps and plans.

Being evil masterminds, Hel and Undurkon would leave some behind, in case the biggest of all plans, complete with plan B, plan C and plan D failed.

So, this would be plan U: Undead plague in the dwarven caverns. And Curly is going to be their leader, until the vampires are necessarily crushed by the dwarven military, some months from now.