Kalawarner

Kalawarner is a Fallen Angel who allied herself with Raynare in her plot to steal Asia's Sacred Gear.

In the anime, Kalawarner attacked Issei after the latter's first errand as a Devil (visiting one of Koneko's regular clients, Morisawa). Although she had the upper hand, she was forced to retreat when Issei activated his Sacred Gear (in its then-Twice Critical state) for the first time.

Later on, she, along with Dohnaseek and Mittelt, fought against Rias and Akeno during the Occult Research Club's mission to save Asia from Raynare.
(Source: High School DxD Wiki)