Child of the Stargazer

The kids stumble upon a young man, sick from exhaustion and hunger. His name is Kosar and he has escaped imprisonment by a demon called Queen Seris.  She wanted Kosar out of the way so she can remain in rule, fearing the 1000 year-old ancient prophecy that must be fulfilled by a 'child of the stargazer.'  The legend states: And on the night of star fall, the child of the stargazer shall come from a faraway land to stand in the Temple of Light.  The demon shall be vanished and the child shall journey home.  After an attack to take back Kosar, the kids start their journey to the Temple of Light.  But when Kosar is taken back by magical means, Diana is taken back with him.  Once there, they have to fulfill the prophecy until the others catch up with them.