An Old Foe
When you arrive, it isn't Katrina, after all. Ad Avis wrote the note, and he's waiting for you! Ask a few questions, then he'll sic his Necrotaurs on you. Don't bother running; you'll get captured anyway. Besides, you have to do so to continue.
You're now in the castle dungeon. Ad Avis taunts you for a bit, but then dawn starts to come, so he flees to his coffin. However, being the villain he is, he didn't bother to make everything escape-proof. If you're a Fighter or Paladin, break the chains. If you're a Wizard, cast Open. If you're a Thief, use your Toolkit.
You can grab the Stake and Hammer if you wish; they open another option up in the next scene, but you die if you chose it, so it's not neccessary. Also, the door's barred from the outside, but you can listen in on the two Goons. Finally, open the Iron Maiden to find a secret passage. You're now inside Katrina's private room.
Open the coffin to see a sleeping Katrina. Kiss her, and she'll wake up. And, believe it or not, she's uber-pissed! She'll chain you to the dungeon ceiling and whip the living shit out of you. Talk your way out of this by choosing any two options, and she'll give you a chance to survive. You must bring her the Dark One's Rituals within three nights, or she'll kill you.
Once she teleports you outside, you'll have to begin your quest for the rituals. And you'd better be quick.
To do the moonwalk, click here. To do something un-Michael Jackson, click here.