She is voiced by Anne Bancroft.
Sedessa and the Nohrin used to live in a land that had thusly become barren and inhospitable, forcing them to relocate to Jhamora, home of the Lockni. The Lockni initially welcomed the Nohrin into their land, but as more Nohrin moved in, there became less space. The leaders of the Lockni proclaimed that no more Nohrin would be allowed to enter Jhamora. Sedessa, enraged, went against King Zahn's orders and massacred the Lochni so that she could conquer their homeland.
Angry at her for not negotiating with the Lockni and instead murdering innocent members of the race, disgracing her people, sending young soldiers to their deaths, and ensuring that his daughter would not be able to take peace for granted, Zahn stripped Sedessa of her status and removed her from the royal family. Sedessa attempts to justify her actions by claiming that the Lockni are savages, despite them clearly being a peaceful people willing to let in outsiders.
Sedessa, seeking vengeance, snuck into Zahn's room to assassinate him and his wife. However, she only succeeded in killing the Queen before Zahn's young daughter Kyla alerted him to Sedessa's presence. In retaliation for her further treachery, Zahn cut off Sedessa's wings and banished her.
Fifteen years later, Sedessa has become the leader of a clan of creatures called the Ando. Sedessa, missing her old wings, keeps several prosthetic wings on her walls, but they fail to allow her to fly. Sedessa quickly betrays the Ando and has them killed before scheming with her second-in-command Raius to usurp control from King Zahn and slaughter the Lockni.
Sedessa sends Raius to vandalize the Lockni's village to provoke a war, but this attempt fails. Sedessa then sends Raius to capture the now-teenaged Kyla. Raius abducts Kyla and brings her to Sedessa's kingdom; Kyla's disappearance causes the war between the Nohrin and the Lockni to restart. Sedessa has Kyla caged, and later holds a ceremony in which she attempts to remove Kyla's wings to get revenge against her father. However, the Lockni Delgo and Filo, aided by the Nohrin Bogardis, interrupt the ceremony and manage to rescue Kyla. Despite this, however, the Nohrin and the Lockni go to war, as the Nohrin still believe the Lochni are responsible.
Sedessa and her army attack once the Nohrin and the Lockni exhaust themselves, and they manage to capture King Zahn. At the castle, Sedessa confronts and berates Zahn for having "weakened" the Nohrin. Delgo arrives to rescue Zahn, and Sedessa has him beaten by her lead Ando guard. Delgo is no match for the guard initially, but he eventually manages to defeat him, leaving Sedessa hanging off the edge of a cliff. As her army is defeated, Sedessa begs Delgo for help. He concedes, but once she has reached safety, Sedessa attempts to kill Delgo. Kyla intervenes and Sedessa stabs her, but Kyla's armor deflects the knife. Sedessa promptly falls to her death when the floor below her collapses.
- She shares similar traits with Zira from Simba's Pride. They both refuse to rejoice and fall to their deaths, however unlike Zira how was willing to die rather then except help, Sedessa begs Delgo to save her, and then attempts to backstab him once he does so, similar to Scar.
- She's also very similar to another villainess, Selina Pereira-Matias. Both are evil sisters to the heroines' fathers, both antagonize their nieces to the point of trying to kill them (which ends with their deaths) and are powerful lords who will sacrifice anyone (including their henchmen) to get what they want. Most importantly, they're the horrifically evil main antagonists, responsible for most, if not all, the bad things that happen in their respective films/series.