From the campaign:
Hmm, the ballistae? They are for the Dragon, of course. What, it wasn’t in your job description? Too bad. You have to first be IN if you want to get OUT. Don’t worry, there will be valiant knights who will come along every so often looking for a fight with the Dragon, and if they like your castle, they just might stay for a bit in case it shows up. Kings will also have a chance passing (let’s not call it something cheesy like fate) and as with the knights, they just might like your castle enough to grace it with their majestic presence.
The Kickstarter campaign is already well over its funding goal with still 21 days left to go.