Damaged returned item. HELP!

[actionjaqson]

Hello, I had a request for a return that I accepted. I finally received the item today and it has either cat puke or cat poop dried on this wooden item. There is also hair stuck in this stuff. What can I do about refunding buyer? If it can be cleaned off at all it may take hours, and this is an antique natural wood (no finish) item. Ebay said to contact buyer and ask why they returned in this condition and ask buyer to agree to a partial refund. I don't want to refund them at all. I believe the item is damaged and I should be able to reject refund request and send the item back to the buyer and they can just keep the mess they created.  Help and suggestions appreciated, Thank you