don't know if it matters what difficulty you're playing, but on tactician co-op arhu has had spider just about my entire game, I'm p sure -- just hit lvl 10 when we quit yesterday.
no spoilers, but you will most likely be finding one of the summons books very shortly, anyway, unless that one's random + I got lucky
oh, also -- right outside arhu's place is some kind of sgt overseeing like 3 guys on a shooting range.
that guy has 1 random book you can check whenever you're up that way.
