Hideaki Anno wrote both the original Japanese lyrics for this song and the unused "Everything You've Ever Dreamed", which was also sung by Arianne and composed by Shiro Sagisu (it later appeared on the Refrain of Evangelion album).
"Thanatos (If I Can't Be Yours)" (stylized "THANATOS-IF I CAN'T BE YOURS-" in Japan) was the theme song used in the continuation and completion of the previous films Death and Rebirth, The End of Evangelion.