Well, it seems I'll stay to live in Castle Skull.....

[Radek]

One way out is through the "spell trap" (a room with flying spells). Go through the door, jump into the poisoning pool (ignore the moving bridge) and use the ladder on the opposite end.
Another way out is through the Goshin area.

[Wyvern]

Thamrys - did you get out yet???

From the well/pool after the water tunnel from the Vamps, you need to go EAST, a little south and then EAST up the stairs - the exit for the castle will be to the west when you come up the stairs (almost directly a level above the well/pool).

Let us know if you've escaped!

Wyv

[Thamrys Greybeard]

I'M OUT! Oh fabrous day, calloo, callay. My exhausted, partly insane, weakened and imp-ridden (but laden with treasure) party is even as we speak getting sozzled in the port tavern. Thank you, thank you (BTW, I get lost driving pretty easily, too!).
Tham

[Sazerac]

Terrific, Thamrys! Glad we were all able to help!

-Sazerac (and Violet!)