What the heck is on this cast iron, and HOW TO REMOVE? Okay, so I just gathered my cast iron dutch oven from my ex, and he apologetically explained that he'd spilled "something" on it. He is an organic farmer who works on cars, so literally: THERE IS NO TELLING WHAT IT COULD BE--from motor oil to transmission oil to yogurt. ONLY--IT WILL NOT COME OFF.  

I have tried:
-traditional methods of cleaning, from water vinegar to soap and water
-AND, here's the most important part: When i tried to simply burn it off, the oven and the house began to smell like acrid poisonous "something." 
-i've even tried "bar keepers friend"

literally sanding down the top seemed to work okay, but honestly, should I just give up? throw it away? will i die if i eat out of this pan?

The substance is sticky and somewhat shiny, like a polymer or plastic based something, and it may have a slightly green tint, though its almost impossible to tell on the black surface of cast iron. in pictures, it just looks like an oil spot.

Oh, and no, I don't have access to a torch.
I used franko's suggestion: oven cleaner. I first sanded it down, and after letting it set, I completely reseasoned it was the answer.