The Sentinels of Magic confiscate spells and tomes they consider ‘dangerous’. It might be worth it to see what they hold in reserve.

METROPOLIS
INVESTIGATION	LOCATION
The Black Codex of R’lyeh	1
Soul-flensing Sorceries of the Seventh Circle	2
The Last Grimoire of Erasmus Jorn	3
Dark Magicks of the Societas Eruditorum	4
Demonaica Lingua: The Demon Tongue Explained	5
The Diary of Hermes Trismegistus	6

Reward:

Arcane Loop Ring