Crystal is a specialist, and has 3 specialist abilities. One is "レーヴァテイル" (Reyvateil) the ability to convert sound into nen. The second is "生きる死ぬ" her scythe, with the ability to consume someone's life force but doing so while cause the scythe to not be able to deal physical damage to him/her temporarily, until the effect wears off for 3 hours. The last one is "ワーレクワイエ' , which means 'hope, wish and desire". She can create any miracle, with the heavy cost of her life force. Netero died, and he placed a seal on crystal, and if he dies, her memories will be restored, along with everyone who is connected to her (which includes gon and killua). Before, pakundo shot crystal with her own memory, causing her to forget who she is, and the ties she made with everyone are forgotten, no one remembered her except netero (cause netero is just extremely poweful and has tricks up his sleeve, plus he paid her to do that.) so, he took her under his wing, and she met them (gon and killua, yes, they meet in hunter exam and hanged out until the yorknew place)again in the Chimera ants arc. When Gon fought against nerefpitou, he was in a "comatose", and the kind and netero died. So many people died because of the Ants, and most ants wanted to turn back into a human. Crystal's first ability also lets her hear the "wishes" of the sound she hears when converting it into her own nen, so she sacrificed all her life force to revive everyone and turn them back to normal / turn back into a human (excluding the king, netero and komugi, cause they didn't want to come back) and she "died". She revived gon back, but now that she's in the comatose, killua and gon go to the zoldyck manor to save Alluka and revive crystal.