Bathory Armor?

[Fellhound]

Excuse my super noob questions but why exactly is a Bathory card so good?

At first I thought it was because shadow element reduced neutral damage and since most monsters deal neutral damage with their attacks, Bathory armor would reduce damage significantly.

As it turns out, ghost element reduces neutral damage, not shadow.

So I'm left wondering why shadow armor is such a big deal...

I assume the Evil Druid card is good for similar reasons. I'm not just getting the reason.

Thanks in advance.