I read a series of books which I don't believe is the Castle Perilous series as those came out at the end of the 80's and I think I read this other series in the mid 80's.
It involved a castle and it was outside of space/time. I think all of the inhabitants were fairly powerful mages. The only key parts I remember was the King was stranded on a water world in one of the books, with no access to magic and finally figures out that there is magic on this world but the Ley lines are under water. The other part is I believe it is the King's brother getting drunk on some voodoo liquor and ultimately saves the day when he pees on something.