three headed dog?

I know I am missing something simple- How or what do I feed the three headed dog or cut the chain- thank you

HInts: The dog likes porridge, but you'll have to make it. Also, once you've helped someone, they'll give you something "strong and lightweight" that will get rid of that chain.

BTW, it took me a while to free that dog. Lots to do beforehand. So just see what there is to do and you'll be able to help him eventually.

And after you've fed the cerebus dog and broken the chain, look at the left paw. There's something else to do there before the dog disappears.