As a young sorceress studying under the faeries, Xandra developed her magical skills... and a jaded view of the faeries' influence on Neopia. The disillusioned Xandra decided to recreate Neopia to match her own vision. Attempting to make a world for Neopets ruled by a Neopet (her, of course), Xandra used the magic she'd learnt from the faeries against them, turning them all to stone.
This curse had consequences that not even Xandra could've imagined: without the faeries' power holding Neopia together, dark creatures emerged and preyed upon the very Neopets that Xandra hoped to empower. In the end, Xandra was thwarted by Hanso and turned to stone with her own magic. Her stone figure is now in the care of Queen Fyora, who still hopes to rehabilitate her most promising pupil.
According to one the Twisted Histories Capsules, in an alternate timeline, she succeeded by killing Hanso and Brynn and managed to keep Faerieland afloat.