Nasira is Jafar's evil sister and is a member of the Villain League. She is also the Big Bad of Aladdin 2.5 Nasira's Revenge. Nasira tried to resurrect Jafar in order to use him as a tool to take over Agrabah and the universe.
Nasira is a sorceress who planned on resurrecting Jafar after his death. She used several magical artifacts and tried to sacrifice Princess Jasmine to Anubis, the Egyptian god of mummification. She nearly brought Jafar back to life but was foiled by Aladdin. Her fate after is unclear.
Nasira's just as terrible as Jafar. She is very vindictive, her strong desire for revenge is backed up by several other negative traits. She is sadistic, violent, manipulative, and very sly. Her only positive trait, loyalty, is marred because she's only loyal to one person, the evil Jafar himself! Not only is she an unpleasant person, but she would even use other people to do her dirty work for her either by using spells or by threatening to endanger their friends. Nasira is very determined and would not stop until she reaches her goal, even if it harmed anyone.
After Jafar is killed off by Aladdin (or was it Iago?) Nasira hears of the event and goes to her lair to contact Jafar from the dead and tell him of the artifacts needed to bring him to life. Jafar warns her of Aladdin and his genie, telling her that they must not be underestimated. After telling him not to worry, she leaves her lair and sets off for Agrabah. Once she gets there, she hypnotisies and corrupts every single guard in the palace. After the sultan and Princess Jasmine were captured, the palace is taken over in one night. Nasira then sends the guards off to find Aladdin and bring him to her, dead or alive.
Once Aladdin is informed by Genie and makes it to the palace to face Nasira, he demands to know where Jasmine and the sultan is. Nasira tells him that she got rid of them since they were no longer needed. She also tells Aladdin that she plans to bring Jafar back and once he is back, Aladdin will not be around either. Genie, wanting to protect Aladdin, confronts Nasira, telling her that Jafar is dead and not coming back. Nasira ignores the comments made and actually pretends to be impressed with Genie and claimed she had heard so much about him, but it was only to catch him off guard. Genie falls for it and after a long pause, Nasira made him disappear with her staff. Genie was then teleported to the Cave of Wonders to be imprisoned again. Aladdin gets alarmed and demands to know what she did with him. Nasira mocks Aladdin and orders the guards to take Aladdin to the dungeon. She also says she'll be there shortly.
Aladdin escapes the dungeon thank to his monkey, gets on his carpet and tries to escape from the palace. He runs into Nasira, and decides to fly at her, possibly to attack her. Nasira starts firing magic at him and missed the first two times, due to Aladdin dodging it. She hits him the third time, knocking Aladdin off the carpet. She leaves, allowing Rasoul to take care of him. Aladdin defeats Rasoul and frees him from Nasira's control.
Aladdin then gains the first artifact that Nasira sought. He goes to the desert and finds a large tent. He enters it and finds a mystic, who is really Nasira in disguise. He asks her where Genie and Jasmine are. She tells him that Genie is in the Cave of Wonders. Aladdin goes to the Cave of Wonders and rescues him. After Abu causes the cave to attack itself by grabbing the red gem (again), Aladdin escapes from the cave to find Nasira (still in mystic disguise) on a camel. She tells Aladdin that Jasmine is near the Pyramids. Aladdin thanks her and flies off. After he leaves, Nasira reveals herself and proudly holds up one of the artifacts.
After saving Jasmine from Anubis, the princess warns Aladdin that she overheard the guards who said Nasira was simply using Aladdin to get the artifacts. Aladdin basically ignores the warning, saying that it hasn't worked yet. After getting a map from Jasmine that led to an ancient city, Aladdin rescues Jasmine's father from the evil sultan that held him prisoner, Nasira appears once more. Aladdin asks her how she found him and the mystic tells Aladdin that the source of her powers were much too difficult to understand, even for him. Nasira reveals herself, which angers Aladdin. He charges at her with a sword, but Nasira quickly paralyzes him with a spell. While Aladdin is unable to move, Nasira takes the other artifacts that he gained from defeating each boss, and opens a portal to her lair.
After she went through it, Abu jumps on Aladdin and smacks him, freeing him from the spell. The portal was closing quickly. Aladdin jumped in at the last moment and found himself in Nasira's lair. He finds her with the ghost of Jafar. Nasira is horrified to see Aladdin and quickly zaps Jafar's ghost, making him larger. After a battle, Aladdin smashes all of the artifacts and kills Jafar again.
As for Nasira, she was last seen floating away, though her fate is a bit unclear. It is assumed she survived.