Eskara was the leader of the Cult of Damnation.
Biography
Bitterness fueled Eskara's rise. The privation of her youth led to a servant's adolescence among Kingsport's knife gangs, subject to countless cruelties. She traded her soul for escape. Eskara remembered every wickedness dealt her, and offered up those responsible--and those who failed to help, and those who resembled them--to the Cult of Damnation.[1]
Wortham
- Eskara(src)

In 1270, she and her cultists attacked Wortham, taking a number of its villagers for sacrifice. Eskara was confronted outside the village by the Shard-seeker, but warned them they were too late, summoning a Putrid Desecrator to deal with them.
The cultists were able to recover a Worldstone shard, and in their lair, conducted a ritual to summon Skarn into Sanctuary. However, the ritual was interrupted by the same hero. Skarn ordered her to slay the intruder in his name, but in this, Eskara failed. With her last breath, she summoned Ifriss the Destroyer.[2]
Damnation's Chosen
- Eskara to the Shard-seeker(src)

After her death, Eskara's soul was dragged down to Hell, where it came to reside in the Citadel of the Damned. Even in death, Eskara continued to serve her master, creating demons from former humans.
Eskara's presence was detected by the angel Kyrel, who led the Shard-seeker into the citadel to confront her. Eskara had not forgotten her death at the hands of her foe, and fought them twice. One, in spiritual form, and a second time, when she was reborn as a demon. This monster too, however, was destroyed. Despite her third death, Kyrel told the Shard-seeker that his kin would keep vigil, as given that Eskara was now a demon, she would inevitably reform in time.[3]
In-game
Eskara is a boss in Diablo Immortal, encountered in the Unseen Lair. She is accompanied by Damned Cultists and Flesh Fiends, and will summon the latter to her side. Her attacks consist of basic melee and ranged attacks.
Eskara re-appears in the side quest "Damnation's Chosen," where she is fought at said quest's end. The first phase is similar to the one in Wortham, though this time, she is accompanied by Immured, Doombound Cabalists, and Flesh Fiends. In the second phase, she is reborn as a Fallen War Matron.