Sidhe is also starting with an S and 5 letters just like Siren and Satyr, making it easy to recognize.
On that account, something short starting with an L would be nice for an alternative to Lord/Lady, but my english ain't well enough to offer suggestions.
I don't like Consul. I could be off here, but to me it sounds like someone you can consult, ask for information, which seems inappropriate.
Likewise, I don't like Justicar either, as it implies some kind of moderator level.
Noble sounds more like the Knight/Dame level to me.