 Pyreflies are a mysterious , naturally occurring phenomenon that heavily influence the events of Final Fantasy X and Final Fantasy X @-@ 2 , as well as the world of Spira at large . Heavily prevalent throughout Spira , these " bundles of life energy " are closely associated with death and other spiritual events and entities by the people of Spira . At high concentrations , Pyreflies are capable of recording memories , sights and sounds . Pyreflies are also associated with many commonplace technological innovations including sphere @-@ shaped recording devices and large , suspended spherical conglomerations of congealed water ( called " sphere pools " ) that serve as the playing field for blitzball games . The pyreflies are also a source of raw energy to empower the giant machina , Vegnagun . Shinra of the Gullwings suggests that the life energy flowing through Spira on the Farplane could possibly be harnessed for the purpose of supplying electricity to a city . In interviews published in the Final Fantasy X Ultimania Ω and Final Fantasy X @-@ 2 Ultimania guidebooks , scenario writer Kazushige Nojima and producer Yoshinori Kitase revealed that Final Fantasy VII and Final Fantasy X @-@ 2 share a plot @-@ related connection , in which the Shin @-@ ra corporation in Final Fantasy VII is founded on another planet after about one thousand years , after space travel became possible , by descendants of Shinra of the Gullwings in Final Fantasy X @-@ 2 . This connection was conceived of only after Final Fantasy X was already finished and realized in Final Fantasy X @-@ 2 riding on the success of the original game and is not reflected in the gameplay or storylines of Final Fantasy VII or Final Fantasy X. 
