Saya and the others are to make their way to Darkness Embrace, the Black World. They have confirmed that the energy “Extra,” important to the worlds, is being lowered there. They are ordered to investigate, but someone’s there waiting for them…
They're crystallizations of Extra 
at the center of each world.
إنَّها تجمُّع من الإكسترا في مركز كُل عالم
Der Weltenkristall ist das
Zentrum einer jeden Welt
Son cúmulos de Extra 
en el centro de cada mundo.
Son cúmulos de Extra 
en el centro de cada mundo.
Les cristaux-monde
È un ammasso cristallizzato di Extra
che si trova al centro di ogni reame.
São coleções de Extra no
 centro de cada mundo.