What gives a vegatable so much power?
Why cant I get a Briarheart?

Dark ritual magic and cheese. Mostly cheese.

Your character level.

I never actually fought a Briarheart. I killed them all by stealing their heart.

But now I'm playing either mage or warrior so I guess I'll be giving them a more head on approach with these chars.

sneak up behind one and pickpocket that briarheart. then see how tough they are.

Briarhearts are pretty tough, but not tougher than me. Their dual wield power attack does 300-500 damage, I think. A melee fighter class might be surprised by how big the damage is, but this is usually not a problem for an archer or a mage because they don't get touched.

Damn, it would have been great if I tried to steal their hearts. But now you spoiled it for me. I forgive.

Spinach.
Or magical transplanted heart plants.
Or the deer heads.

I knew it. They wouldn't believe me.
Dairy products can't enhance your vegetable heart they said. Too much risk involved they claimed