Go right from the fountain, jump down for the terrace below and down again to the other. The struggle with the boss - Mahasti, awaits you. You must have an extra weapon in this skirmish, otherwise you don't have any chances to defeat Mahasti. If you are not equipped with extra weapon, return back to fountain's surroundings. Jump over the rail and land on the bottom of the courtyard. You will find the rack with the weapon there. After equipping yourself return back to the fight arena with Mahasti.
Mahasti is the strong and nimble rival. She is attacking with series of blows, and you are not able to block them all. The Mahasti kick is able to dump you from the platform and the fall from this height always ends with death. So try to initiate your attacks standing at the side of the wall, so the not blocked kick will squeeze you in the wall at worst but not throw overboard the arena. After executing the series bumps Mahasti will rest for a moment so this is time for the counter-attack, use it. The rival can't block all the air attack so try this method.
You will clash with Mahasti's blade during the fight you will begin wrestle with knives. You have to press then the left mouse button fast, to "overpower" Mahasti. After inflicting wounds which takes off about 1 bar of the opponent's energy, you are entering the second round of the fight. You are changing into the Dark Prince and Mahasti is escaping after every single attack to the opposite end of the yard. You have to run after her, circulating backyard on the left or on the right side.
During running after Mahasti you are hooking platforms where illusions are placed. Eliminate them, because balls of the sand from their bodies are regenerating your energy. After getting Mahasti you have only one moment to use Daggertail. After few blows the Boss is escaping to the most far-away corner again. How to stop her? Before jumping on the roof with her, use the Eye of Storm power so you will slow down the time. Mahasti will be still escaping from you but before she will manage to do in slow motion you will wound her quite a lot. A few such actions and you have her on the fork.
You will cross the knives' blades in the last phase of the skirmish again (press the left mouse button fast), after which Mahasti will fall down the roof and she will die. Farah will show up in the arena after the fight. She is no fancy with the Dark Prince form. Your explanations will increase her fury only. He will shoot the arch at you but she will fail luckily. She will escape after a while.