I wrote the riff first and walked around with that in my head for a few days. Then the rest of the song sort of just came to me all at once, and I recorded it with ad lib vocals for the verse and chorus. I ended up liking the verses I sang but not liking the chorus. So I shelved it and moved on.
I was reading the Tibetan book of the dead when I came across Vajrayana: Vehicle of Indestructible Reality. Most of the time when I’m reading the Book of the Dead I can barely keep up with what I’m reading, but that concept just stuck out to me. I was actually learning how to pronounce Vajrayana when I had the idea of singing it like a mantra for the chorus of Thunderbolt Diamond. It immediately changed the song for me. I wish I could explain the concept of Varjayana but I'm not a good teacher or a Buddhist and my grasp of sacred cycles is tenuous at best. I just know the chorus worked for me when I changed it to:
(Va)Vajrayana
Oh my soul
How it relates to the verse is for you to decide.