Spoilers: Character background and the premise of Dechala's campaign.

Mistress of the Tormentors
Dechala pursues pleasure and freedom for herself while imposing suffering on others. Her followers include Thralls whose bodies and wills are consumed in her service. The Tormentors move from one conquest to another, leaving their victims to pay for their leader's excess.
Her altered body has a serpentine lower half and a sword in each of her many hands. The speed and violence of her attacks reflect the same cruelty that governs her warband.
The Denied One
Dechala resembles a daemon, but she has not attained Daemon Princess status. She remains the Denied One in Total War: Warhammer III. Her title marks a distinction between the power she already possesses and the ascension she still lacks.
Her warband in Immortal Empires
Her campaign expresses that identity through Thralls, Pleasure Palaces and Decadence. Conquest supplies the resources for her indulgence. Immortal Empires leaves the course of that conquest to the player.
Six swords and a serpentine body
Tides of Torment presents Dechala as daemonic in form and not in essence. She is the head of the Tormentors, a warband that mesmerises the people it conquers and works them as Thralls until they are spent, then moves on. The store page is blunter about the body: more daemonic serpent than human, a sinuous length rising to a six-armed torso, a sword in each hand. Beauty and horror are the same silhouette.
The campaign turns that waste into a cycle. Captured settlements can become Thrall Camps. Productivity falls as the people are used up. Pleasure Palaces and Decadence are what the faction builds on top of that spending. Pillars of Cruelty, Slaanesh boons, and daemons recruited in the moment are the tools around the camps. The lord page is the place for the order of those buildings. The cruelty is the reason they exist.
Still the Denied One
The title is the point of the character in this pack. She looks like a daemon and leads daemon-touched armies. She has not been made a Daemon Princess. The Tides of Torment answers keep her Denied after the pack’s release. Ascension is withheld. The campaign does not hand it over as a reward track.
She begins at the Hidden Landing in the Cathayan Hinterlands. That is an Immortal Empires start, a place to spend the first Thralls, not a claim that Cathay’s history has already ended in her favour. The Masque, added free in Update 7.0, is the other new Slaanesh lord of that season. N'Kari remains the base-game Keeper of Secrets, with a novel behind his hatred of Tyrion and Teclis. Dechala’s warband is the one that eats settlements.
Update 9.0 lets Archaon subjugate her and pass the Tormentors’ regions to a Slaanesh vassal. The Denied One stays denied. A sandbox defeat is not the ascension the title says she has not received.
Dechala the Denied One: gameplay and availability · More character stories
Sources
- Tides of Torment: Meet Dechala — CA — community.creative-assembly.com
- Tides of Torment — Q&A answers — CA — community.creative-assembly.com
- Tides of Torment: Meet Dechala — Total War — totalwar.com
- Dechala — Tides of Torment — Total War — totalwar.com
- Tides of Torment Q&A — Total War — totalwar.com
- Update 9.0 release notes — Total War — totalwar.com
- Immortal Empires DLC Ownership Guide — SEGA — support.sega.com
- Dechala — Tides of Torment — CA / SEGA on Steam — store.steampowered.com
- Update 9.0 Release Notes — CA — community.creative-assembly.com