Hell Bent (original) Leigh Bardugo

Find a gateway to the underworld. Steal a soul out of hell. A simple plan, except people who make this particular journey rarely come back. But Galaxy “Alex” Stern is determined to break Darlington out of purgatory―even if it costs her a future at Lethe and at Yale.

Forbidden from attempting a rescue, Alex and Dawes can’t call on the Ninth House for help, so they assemble a team of dubious allies to save the gentleman of Lethe. Together, they will have to navigate a maze of arcane texts and bizarre artifacts to uncover the societies’ most closely guarded secrets, and break every rule doing it. But when faculty members begin to die off, Alex knows these aren’t just accidents. Something deadly is at work in New Haven, and if she is going to survive, she’ll have to reckon with the monsters of her past and a darkness built into the university’s very walls.