Mahasti is a trusted General of the Vizier. She is responsible for embedding the Daggertail in the Prince's left arm just before the Vizier killed Kaileena and released the Sands of Time. It appears that the Sands have not been so merciless in destroying her appearance as they were with the other characters, although they have granted her strength and extraordinary agility. She imprisoned many women in a Brothel and confronted Farah and the Prince. Realizing she was outmatched, she fled. Halfway through his fight, the Prince turns into The Dark Prince, who fights with her and pushes her off a ledge, ending her life, ignoring her warning that he would fail to defeat the Vizier; in fact, he even says after she dies: "If I got Sands for every time someone said that to me - oh wait -" then after a brief pause in which Mahasti's form comes up as Sands and the Prince absorbs it, "- I do." She wields two jagged swords and fights much like Shahdee in Warrior Within.
Mahasti seems to have been less affected by the Sands than the other three generals since she kept her ability to talk and seems to act for herself, the reason for that is unknown.
A strategy similar to Crow Master can be used on Mahasti. As is grabbing her, staying a safe distance from her is the safest strategy, whilst bouncing off of walls into her for an attack that lets you out of her range before she counters, as she sometimes defends against the attacks. Another option is to jump over her, and then use the dagger to slice at her, then repeat. If she starts overpowering you, block, and run away. Be wary of her powerful kicks, which can shoot you off the block the two of you are fighting on.
As the Dark Prince, the battle becomes less linear, and takes up more of the battlefield. The easiest - and probably the only - way to kill her is to use the Sands of Time to slow time down, and hit her before she leaps away from you. Once she lands on the other side of the battlefield, there should be a minion on your way to her, letting you regenerate health and sands.
Keep up your onslaught until Mahasti goes down. Then your story continues.