The seller is offering the item of jewellery on the online marketplace after an apparent bad break up.
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He alludes to his former lover with some colourful storytelling.
The posting is based in Newport.
The advert on Gumtree
He cites the breakdown of the relationship involving a problem with the "Well Devil, a devil that dwelled in the depths of, well, wells...".
The seller goes on to explain how "one day Satan awoke from its slumber and said 'listen here, mere mortal... I *SATAN* (can't use her real name for legal reasons) don't like you'."
The seller is asking for serious offers only, despite his tall tale and crude "ring is size fat" guide, as the ring is 1/4 carat gold, Wales Online reports.
There's a price at the top of the Gumtree page, indicating the seller wants £200 for the ring.
He also adds a disclaimer, stating "although worn by Satan herself it does not possess any magical powers or any black magic. Cannot guarantee it's 100% safe to be worn by those of faith".
If you're in the market for an engagement ring, and you don't mind the idea of "Satan's" second-hand jewellery, you can pick up this one on Gumtree.