The Vampire and the Lich

History
Anastasia and Aiko Keane were once a pair of ambitious Nyfian wizards

Anastasia was severly injured and killed, so Aiko threw herself into her studies of necromancy to try and save her, eventually managing to bring her back as a vampire, but not before her exploration into necromancy transformed her into a lich.

Anastasia
Human wizard, now a vampire spellcaster

Aiko
Half-orc necromancer, now a lich

Her phylactery is the gates to Avernus, to destroy her that seal must be broken, unleashing the devils of the nine hells onto the prime material plane.

Currently the cult of Tiamat is trying to break those gates in order to release Tiamat from her imprisonment, which is why Anastasia's upped her game in her search for Aiko.