"Showdown at Hollow Bastion" is a musical theme composed by Yoko Shimomura. It is first heard in Kingdom Hearts II.
"Showdown at Hollow Bastion" is heard as a part of "Fantasia alla Marcia for piano, chorus and orchestra"
Disc 2, Track 23 in the Kingdom Hearts II Original Soundtrack
Disc 6, Track 1 in the Kingdom Hearts Original Soundtrack Complete
Disc 4, Track 1 in the Kingdom Hearts HD 2.5 ReMIX Original Soundtrack