This was 12 years ago, so it's possible that I don't remember the details correctly. I thought that "self" could not be selected for fire damage, but looking up videos of spellmaking in Oblivion this seems to be possible.

I do distinctly remember being unable to recreate that one fire spell, though. Perhaps it was not possible to set damage to 0 in Oblivion? That was part of why the spell became so cheap and allowed for extreme duration.