Nick is an 800 year old vampire. If you need someone who remembers a historical figure, someone who's bloody old, or a vampire, he's your friend. Or if you need someone to learn something and only have, say, their blood hanging around. FK vamps have a fun thing with blood that's in his info page.
Fiona can still CUT ANYTHING, see the strings that hold reality together, and has some demonic fu that she keeps locked up pretty well. If you want a mythological figure to have business on island, she's a good excuse.
Liir can still see the past, do some magic (he's getting better at stuff!), and fly a broom. He's also good for any Ozian madness.
Derek is still BAU and handyman.
Geoffrey is good for all your madness and Shakespearean needs.
Abby Irene will happily provide thaumaturgical forensics.
Re: Plot spare parts
Fiona can still CUT ANYTHING, see the strings that hold reality together, and has some demonic fu that she keeps locked up pretty well. If you want a mythological figure to have business on island, she's a good excuse.
Liir can still see the past, do some magic (he's getting better at stuff!), and fly a broom. He's also good for any Ozian madness.
Derek is still BAU and handyman.
Geoffrey is good for all your madness and Shakespearean needs.
Abby Irene will happily provide thaumaturgical forensics.