So. I've been thinking about, and looking up info on the Dark Elf in the Magnetic Cave. Here's what I found:
1. If you don't have the whisperweed, you don't fight the Dark Elf. You merely enter a scripted battle with an invincible facsimile.
2. Invincibility is used for bosses you can't beat. Infinite HP is not a thing in this game.
3. If you have the whisperweed, and you don't have metal equipment on, you can do damage to the Dark Elf...
Therefore, it stands to reason, that if you keep your HP up, and you can take enough of his HP before he casts Tornado, you can beat the Dark Elf without Edward's help. Is there anything I'm overlooking that might make me wrong?