I've discovered what Lilith was after in the Necropolis of the Firstborn. I must reconvene with Neyrelle at the Horadric Vault.
Phase42
Phase42Description
The pursuit of Lilith in Fractured Peaks draws to a close. She obtained a key of some kind from the murdered corpse of Rathma, but to what end? Meanwhile, Neyrelle took her mother's corpse to the Horadric Vault for a proper burial.