Which hero do you like?

With Vampires and Bone Dragons, Haven won't last long! And we'll cast a plague on you – you won't win, your undead mental tricks won't work!

Illusions work :) And there's also teleportation. And, as Optimal correctly noted, there are good potions with viscous liquid (by the way, this is also considered a Haven spell!)
And if the dragons get too close... (sighs, "