The Library is filled with books, torches, tables, humans, Golems, and the occasional Noble. It's mostly safe to explore in human form, but the Nobles can be tough to deal with when underleveled.
The Princess can be found in one of two closed rooms on either side of a special chamber.
She can cast any of the following level 3 spells: FIRESTORM, ICE, SHOCK, GLOW, and HEAL. Her spell power is no worse than that of a Solomonar, but her huge health and mana pools allow her to cast repeatedly.