From the publisher's website:
The Freedom City Atlas is a series of products intended to flesh out and further detail the award-winning Freedom City setting for Mutants & Masterminds. In this series, we "zoom in" to look at different facets of Freedom City in detail, providing you with all the information you need to know about them to make them centerpieces in one or more adventures set in the city of heroes.
The Scarab's Lair is a kind of comic book archeology, looking at the abandoned secret lair of the Scarab, hidden beneath Pyramid Plaza (detailed in Freedom City Atlas 1). Unlock the secrets of the Scarab, eternally reincarnating Egyptian psychic! With pages of floor plans and cutaway diagrams, you can use The Scarab's Lair for a new incarnation of the Freedom City hero, a base for new heroes (or villains!) or a place for your heroes to explore, looking for clues left behind by one of their heroic predecessors. Enter The Scarab's Lair, if you dare!