The Final Wand can grant wishes, but the person who uses it will lose something precious to them, with the possibility of their own life being the thing that they lose. If the user has nothing left to lose, then they will automatically be sacrificed upon using the Final Wand.
The wand can also be used as a weapon, especially for defeating Beasts.
The Final Wand was kept hidden in the Jewel Palace, but was stolen by the Joker for her own dark schemes. She sends it to Luea, and deceives her into believing that filling the wand with Jewel Power will bring back Lillian; this makes Luea unintentionally open the Door of Chaos.
When the Joker is revealed to be Lady Lecter, she is regretful that her actions didn't have the results that she desired and instead led to Lady Diana's sacrifice. When Lady Lecter gets possessed by a Beast, she stabs herself with the final wand to protect everyone from the Beast, which also results in her own death.
In episode 50 of Lady JewelPet, Momona and Cayenne use the Final Wand to restore the land and save everyone's lives. They both lose their memories and life in JewelLand, continuing their normal life on Earth.