The vampire Lestat is awakened from decades of slumber by the sound of a heavy metal band which he proceeds to take over as the lead singer. Achieving international success and planning a massive live concert, Lestat is approached by Marius, and warned that the vampires of the world will not tolerate his flamboyant public profile.
Jesse Reeves, a researcher for the paranormal studies group Talamasca, is intrigued by Lestat's lyrics and tells the rest of the group her theory that he really is a vampire. Her mentor, David Talbot, takes her aside and tells her they know he is and that a vampire called Marius made him. He also shows her Lestat's journal that he recovered and is now in the Talamasca library. In a flashback to his origins, Lestat recalls how he awoke Akasha, the first vampire, with his music. Jesse tracks him down to a London vampire club where he saves and confronts her. She later goes to Los Angeles for the concert and gives him back his journal. The two spend some time together and Lestat shows her both the horrors and the perks of being a vampire. Showing him that she's not scared of him Jesse stays with Lestat as she sees how lonely and miserable he is. She asks him to turn her as she reveals that it's her dream to be a vampire, but he refuses as he won't do it to her. The more time they spend together, the closer they become and soon Lestat and Jesse start to fall in love. Meanwhile, Akasha is awakened by Lestat's new music. She arrives and torches the club, and all the vampires inside, who want Lestat dead.
At the concert in Death Valley, a mob of vampires attack Lestat and Marius. Akasha bursts through the stage and takes Lestat with her as her new King. The two vampires then proceed to have a sort of sexual intercourse in Akasha's home where they mutually feed on one another, during which time Lestat becomes spellbound by Akasha and is forced to obey her. Empowered by Akasha's blood, Lestat and the Queen confront the Ancient Vampires at the home of Maharet, Jesse's aunt, who is an Ancient Vampire. The Ancient Vampires were planning to kill Akasha, to save the human world from demise. Akasha then commands Lestat to kill Jesse, as The Queen sees her both as an enemy and as food, as she is Maharet's mortal niece; Maharet and Akasha became mortal enemies before they were turned. Queen Akasha also wanted to make an example out of Jesse because Jesse dared to stand-up to her and to put fear into the other vampires. Lestat ostensibly obeys the Queen, but afterwards he quickly comes to his senses and is released from her power. He then very angrily turns and begins to drain Akasha's blood with the help of the Ancients. Mael and Pandora are killed by Akasha's power. Armand is almost killed, but is saved as The Queen's powers diminish. Maharet is the last to drink Akasha's blood, and thereby ends up becoming a marble "statue". Maharet then becomes the new Queen Of the Damned.
Lestat then turns and walks to where Jesse is lying lifeless, and cradling her in his arms, gives her his blood, turning her into a vampire. Jesse, now a vampire, and Lestat then return the journal to the Talamasca, and walk away, among mortals, into the night. As they exit it is shown that they are now a couple and hold hands while Marius enters the Talamasca. The film closes with a scene of David reading the journal as Marius's voice catches his attention, cheerfully saying, "Hello, David".

Question: Why were the Ancient vampires planning to kill Akasha? 
Answer: To save the human world from demise.