Shiva is available until... errr how can i say it without spoiling it.... errr i'l just say until you fight Archeoavis... If you fight something called archeoavis then don't progress through the game anymore till you get her. If your already at the library of ancients then defeating shiva will be easier than defeating the random encounters your currently errr encountering. She's in Walz castle, just take a right upon entering and take the staircase, then take the exit to the lower right of this room. Follow the path right, up and left till you find a waterfall, enter it and follow the path to the top room and she'll be sat in the center waiting for you.

Biblos... this is gunna test my memory... ummm i'm taking it you fought Ifrit already??? Once you've fought Ifrit, the bookcase blocking your path will let you pass. If you enter a room with no visable path through, then go touch every floor panel in the room (can't remember if you simply have to step on a certain space or whether you have to press X when stood on the space) You'll also reach a room where there is a stairway that leads into a bookshelf, you'll have to climb up and press X to initiate a fixed battle. That leads you into a save room which if you follow out should pass you through another room before entering the room with Biblos. Phew i hope thats right... :s