If the Siege and Investiture... had the more ambitious orchestration, Magna is the most theatrical of the songs, followed closely by the Blue Oyster Cult song. Robby Krieger of The Doors plays lead guitar on this and the following song.
The impressive personnel roster is made of:
Band members
Eric Bloom – vocals
Albert Bouchard – guitar, percussion, vocals, associate producer
Joe Bouchard – keyboards, backing vocals
Allen Lanier – keyboards
Donald Buck Dharma Roeser – guitars, vocals

Session musicians
Phil Grande – guitars
Tommy Zvoncheck – keyboards
Kenny Aaronson – bass
Thommy Price – drums
Joey Cerisano – vocals
Jon Rogers – vocals
Jack Secret (aka Tony Geranios) – backing vocals
Shocking U – backing vocals on In the Presence
Daniel Levitin – guitar sounds (uncredited)

Guitar Orchestra of the State of Imaginos:
Marc Biedermann (lead guitar on I Am and In the Presence)
Kevin Carlson
Robby Krieger (lead guitar on tracks Magna... and Blue Oyster...)
Tommy Morrongiello
Aldo Nova
Jack Rigg
Joe Satriani (lead guitar on The Siege and Investiture...)