A library between planes that is open only to dragonkin and their friends. It is managed by the mysterious Mattai. Within, there seems to be books about anything and everything. Its contents and form seems to shift as an individual’s understanding and relationship with magic changes.
Bane referred to her and The Library Between as “the belly of the beast”. When Arythas entered the library, he could tell that something is distinctly wrong with this place and it is incorrect in a way that makes his soul squirm.